A. parts of a flower B. food for a developing embryo C. the embryo of a seed D. the male reproductive parts of a plant (Answers - C )

60. To reduce competition between a parent plant and germinating plants for scarce resources such as light, soil and water, seeds must:

A. be dispersed B. develop C. be dormant D. have the same niche (Answers - A )

61. The basic hereditary factor that is inherited from one generation to the next is the:

A. sperm cell B. egg cell C. gene D. zygote (Answers - C )

62. The characteristic, or version, of a trait that an organism has is called its:

A. phenotype B. genotype C. gametes D. DNA (Answers - A )

63. In pea plants, the allele for the tall characteristic of height is dominant over the allele for the short characteristic. Tall pea plants are crossed with short pea plants, resulting in 149 tall plants and 153 short plants. Based on these results, the genotype of the tall plant is:

70. A normal bean seedling that has the ability to produce chlorophyll doesnít when grown in soil lacking magnesium. This demonstrates:

A. that a mutation probably occurred, preventing chlorophyll production B. natural selection C. the influence of the environment on gene expression D. the need for light in chlorophyll production (Answers - C )

A. receive stimuli from the external environment B. bring materials from the external environment into contact with all the cells of the organism C. break down nutrients so that the cells can use them D. remove solid waste materials from the digestive system (Answers - B )

6. The change of digested food into the living matter of the cell is called:

18. A student measures the length of a paramecium to be 100 µm under low power (100X magnification). He switches to high power (400X magnification) and measures the paramecium. What is the size of the paramecium under high power?

A. 25µm B. 100µm C. 400µm D. 4,000µm (Answers - B )

19. How many millimeters is a cell that measures 675 micrometers?

A. 0.675mm B. 6.75mm C. .000675mm D. 675mm (Answers - A )

20. The field of view of a microscope is 1,000 micrometers. A student counts five cells of equal size going across the field of view. How long is each cell?

A. 20µm B. 200µm C. 500µm D. 5,000µm (Answers - B )

1. Who was the first person to study living cells?

Answer: Anton van Leeuwenhoek was the first to see living things such as bacteria and animal-like protists. Although Zacharias Janssen preceded Leeuwenhoek and made a compound microscope, he did not use it to study living things.

2. Who named the cell?

Answer: Robert Hooke used a compound microscope to observe cork from the bark of the cork oak tree and saw small box-like structures that he named cells.

3. Who discovered the nucleus?

Answer: Robert Brown discovered the nucleus while working with plant cells.

1. Why is a microscope necessary to study cells?

1. A microscope is needed to see cells because they are too small to be seen by the naked eye.The tools most often used to magnify cells are the compound and electron microscopes.

2. State the main concepts of the cell theory.

2. The cell theory states that the cell is the basic unit of structure and function in all living things. Also, new cells arise only from previously existing cells.

3. Explain the concept of unity.

3. All organisms are composed of cells, function as a result of their cells, and produce new offspring by cell reproduction. These concepts of the cell theory serve to unite all living things.

4. Outline the structural hierarchy that is found in all organisms.

4. The structural hierarchy that is found in all organisms builds on the concept that the cell isthe basic unit of structure in all living things. Similar cells combine to form tissues, similar tissues combine to form organs, organs work together to form organ systems, and all the different organ systems combine to form the organism.

5. Why are viruses considered exceptions to the cell theory?

5. Viruses do not have the cell structures common to most cells. Most biologists do not consider them living things.

1. Cell membrane

The outer boundary of the cell protects the cell, controls what goes in and out of the cell (selective permeability), and holds the cell together.

2. Nucleus

Contains chromosomes, which have DNA and control the heredity of the cell. Controls the reproduction of the cell. A nuclear membrane surrounds the

chromosomes.

3. Nucleolus Found inside the nucleus; associated with the production of ribosomes.

4. Vacuoles Storage sites for food or water.

5. Cytoplasm The liquid part of the cell found within the cell membrane. The organelles float

inside the cytoplasm.

6. Centrioles

Centrioles are cylindrical in shape and function in the reproduction of the cell.

7. Chloroplasts

Small oval-shaped structures containing the green pigment, chlorophyll. They produce glucose during photosynthesis.

8. Cell wall

Found in plant cells outside the cell membrane. The cell wall is made of cellulose, which is rigid and nonliving. This organelle gives the plant cell support and shape.

1. Define the term organelle.

Answer: Organelles are the parts that make up a cell.

2. Name the organelles that are found in most cells?

Answer: The organelles that are found in most cells are cell membrane, nucleus, nucleolus, vacuoles, and cytoplasm. Note: Mature red blood cells do not have a nucleus and are an exception.

3. What is the function of the nucleus?

Answer: The nucleus contains chromosomes, which have DNA and control the heredity and reproduction of the cell.

4. What is the function of the cytoplasm?

Answer: The cytoplasm is the liquid within the cell membrane in which all parts of the cell float.

1. How are animal cells different from plant cells?

1. Animal cells have two centrioles and many small vacuoles. Plant cells do not have centrioles, but they have chloroplasts and one or two large vacuoles.

2. Why must the cell membrane be selectively permeable?

2. Selective (or semi) permeability is the ability of a cell membrane to control the movement of materials into and out of the cell. Materials that enter the cell are water, food, and oxygen, which are needed by the cell to perform its life functions. Materials that leave through the cell membrane are wastes such as carbon dioxide. Also, the cell membrane prevents harmful organisms and substances such as poisons, viruses, and bacteria from entering the cell.

3. How is the cell membrane different from the cell wall?

3. The cell membrane is a living part of the cell and is found in all cells. The cell wall is nonliving and made of cellulose. It is found only in plant cells.

4. Why must a plant cell have chloroplasts?

4. Chloroplasts contain the green pigment, chlorophyll, and function in photosynthesis for the production of food.

1. How does the cell membrane differ from the nuclear membrane?

Answer: The cell membrane is the outer boundary of the cell; the nuclear membrane surrounds and protects the chromosomes of the cell.

2. What is the function of ribosomes?

Answer: Ribosomes are sites for protein synthesis. Proteins are needed for growth, repair, and reproduction of new cells.

3. Why are mitochondria important for a cell?

Answer: Mitochondria are the energy factories of a cell and are associated with cellular respiration. In the mitochondria, oxygen is used to chemically release energy that is stored in food. During this process, the waste products carbon dioxide and water are produced.

1. Explain the fluid mosaic model of the cell membrane.

Answer:1. According to the fluid mosaic model, the cell membrane consists of two layers of lipid with proteins spread throughout the layers and in between the layers.

2. How is the Golgi body different from the endoplasmic reticulum?

Answer: 2. The Golgi body has flattened membranes that look like plates stacked on top of each other, and their function is to package proteins. The membranes of the endoplasmic reticulum form a canal-like network within the cell that functions in the transport of materials. Some endoplasmic reticulum membranes have ribosomes attached to them and are referred to as rough endoplasmic reticulum. Ribosomes are never attached to the Golgi body.

3. Why does the breakdown of the lysosome membrane result in the death of a cell?

Answer: 3. Lysosomes contain digestive enzymes for the breakdown of food. If the lysosome membrane breaks, the enzymes it contains leak into the cytoplasm and digest the organelles of the cell. This results in the death of the cell. Thus, lysosomes are sometimes called the “suicide sacs” of the cell.

4. Describe the process of endocytosis.

Answer: 4. Endocytosis is a process by which the cell membrane forms a small pocket or pouch that surrounds and engulfs food particles that are too large to pass through the membrane; this pocket is called the endocytotic or pinocytotic vesicle.

Diffusion:

The movement of any molecule (except water) from an area of high concentration to an area of low concentration.

Osmosis:

The movement of the water molecule only from an area of high concentration to an area of low concentration.

1. What is molecular transport?

Answer: Molecular transport is the movement of molecules across a membrane.

2. Define passive transport.

Answer: Passive transport is the movement of molecules from areas of high concentration to areas of low concentration. No energy is required.

3. Define active transport.

Answer: Active transport is the movement of molecules from areas of low concentration to areas of high concentration. Energy is required.

1. How is molecular transport different from circulation?

Answer: 1. Circulation is concerned with the movement of materials such as food, oxygen, and water from the environment to all cells of the organism. Molecular transport explains how these materials get into the cell.

2. Why can some molecules pass through a cell membrane while others cannot?

Answer: 2. Small molecules can pass through a cell membrane; large molecules cannot.

3. How is diffusion different from osmosis?

Answer: 3. Diffusion is the movement of any molecule (except water) from areas of high concentration to areas of low concentration. Osmosis is the movement of water molecules from areas of high concentration to areas of low concentration.

1. All the following are concepts of cell theory except:

A. The cell is the basic unit of structure in all living things. B. The cell is the basic unit of function in all living things. C. New cells arise only from previously existing cells. D. All living things have chloroplasts. Answer: D

10. Select the description that best illustrates the structure of the cell membrane.

A. three layers: protein/lipid/protein B. three layers: lipid/protein/lipid C. two layers of protein D. two layers of lipid with proteins spread throughout the layers and in between the layers Answer: D

11. Proteins are needed by a cell for:

A. growth and repair B. energy C. transport D. respiration Answer: A

12. Semipermeability describes the ability of the cell membrane to:

A. transport materials from one location to another within the cell B. control the movement of materials into and out of the cell C. actively manufacture vacuoles and lysosomes D. hold the cell together Answer: B

Answer: Living things are classified into logical groupings to make it easier for biologists to study them.

2. What is meant by diversity?

Answer: Diversity refers to the millions of different kinds of living things that exist on earth.

3. What is phylogeny?

Answer: Phylogeny refers to the evolutionary development and history of a species of organism.

4. How is the three-domain system of classification different from the six-kingdom system of classification?

Answer: The three-domain system of classification includes Bacteria, Archaea, and Eukarya. Domain Eukarya is subdivided into the following four kingdoms: Protista, Fungi, Plantae, and Animalia. The six-kingdom system of classification includes Eubacteria, Archaeabacteria, Protista, Fungi, Plantae, and Animalia.

5. List the taxa of classification from the largest grouping to the smallest.

Answer: Viruses are not classified into a domain because many biologists do not consider them living things. Outside a cell, viruses do not perform life functions such as respiration, ingestion, transport, excretion, and locomotion.

2. Which life function is a virus capable of performing?

Answer: A virus is capable of reproduction only when inside a host cell.

3. What is the structure of a virus?

Answer: A virus consists mostly of genetic material (DNA or RNA) surrounded by one or two protein coats.

1. Describe the life cycle of a virus.

Answer: 1. A virus invades a cell’s nucleus destroying the cell’s DNA. The virus then inserts its own genetic material and takes over the life functions of the cell. The virus begins to replicate within the cell. Eventually, the cell bursts and dies—releasing the newly formed viruses, and the process can begin again.

2. Why can’t a human catch a cold from a dog?

Answer: 2. A human cannot catch a cold from a dog because the virus that causes a cold in dogs is unable to insert itself into human cells.

1. List the major characteristics of the domain Bacteria.

Answer: Single-celled organisms (unicellular), primitive cells dating back at least 350 million years, with prokaryotic cells.

Answer: Heterotrophs are organisms that obtain food for energy, growth, repair, and reproduction of new cells. Autotrophs are usually green plants that make their own food by the process of photosynthesis.

1. How can we distinguish between members of the domain Bacteria and the domain Archaea?

Answer: 1. Bacteria have cell walls that contain peptidoglycan, and they respond to antibiotics. Archaea have cell walls that lack peptidoglycan, and they do not respond to antibiotics.

2. Why are Bacteria considered primitive organisms?

Answer: 2. Bacteria are considered primitive organisms because the current-day Bacteria are similar to those that lived 350 million years ago. These organisms are prokaryotic, which is a primitive cellular characteristic.

3. A student found a colony of organisms in a salt lake and noticed that they had the following characteristics: no nuclear membrane, no peptidoglycan in their cell walls and they lacked the ability to manufacture their own food. Where should the student classify these organisms?

Answer: 3. These organisms should be classified in the domain Archaea. The lack of a nuclear membrane indicates that the organisms are prokaryotic. Archaea is the only domain with organisms that are prokaryotic, lack peptidoglycan, and are found in salt lakes.

4. Which evolved first, viruses or Bacteria? (Review the section on viruses before answering this question.)

Answer: 4. Bacteria evolved before viruses. At first it might seem that viruses evolved before Bacteria because they are not cells and do not perform life functions except for reproduction. However, this is not the case. To reproduce, a virus must have a host cell to invade. The host cells must be there first for viruses to reproduce.

1. List the major characteristics of the kingdom Protista.

Answer: Protista are mostly unicellular organisms with animal-like, plant-like, or fungus- like characteristics. Protists can be heterotrophic or autotrophic. All protists are eukaryotic.

2. How do amoeba, paramecia, and trypanosoma differ in their mode of locomotion?

Answer: Amoeba move with the help of pseudopods, false feet that are cellular extensions of the organism and constantly change shape. As a result, the amoeba is an organism that does not have a definite shape. The paramecium is covered with tiny hair-like structures called cilia that are used to propel the organism back and forth in the water. Trypanosoma has a tail called a flagellum that it whips back and forth to propel itself.

3. What are the characteristics of slime molds?

Answer: Slime molds are unicellular organisms. Some have only one nucleus (cellular slime molds); others have many nuclei (acellular slime molds). In many ways slime molds resemble a huge amoeba. All slime molds are nongreen and heterotrophic.

1. How are prokaryotic cells different from eukaryotic cells?

Answer: 1. Prokaryotic cells do not have a nuclear membrane and are characteristic of organisms in the domains Bacteria and Archaea. Eukaryotic cells have a nuclear membrane and are characteristic of organisms in the domain Eukarya.

2. How are the Euglenophyta and Chlorophyta different from animal-like protists?

Answer: 2. Euglenophyta and Chlorophyta are phyla, containing organisms that have plant-like characteristics. They are green, autotrophic, and are capable of photosynthesis. The animal-like protists are nongreen and heterotrophic.

3. How can we distinguish between green algae and Archaea?

Answer: 3. Green algae are in the kingdom Protista, and they are eukaryotic with cell walls that have cellulose. Archaea are prokaryotic and have cell walls lacking cellulose.

1. List the major characteristics of the kingdom Fungi.

Answer: Fungi are eukaryotic, have cell walls made of chitin and their cells lack chloroplasts. They are heterotrophic, decomposers, and unicellular and multicellular organisms. Fungi are broken down into several phyla, with organisms classified according to methods of reproduction.

2. How do Fungi obtain food?

Answer: Many fungi are heterotrophic and obtain their food by absorption from decaying vegetation.

3. Describe the structure of a fungus.

Answer: Fungi are composed of thread-like filaments called hyphae that are attached to rhizoids on the bottom end. Rhizoids anchor the organism to its food source. The top of the organism often forms a reproductive structure called a sporangium.

4. What is a parasite? Give an example of a parasite that is a fungus.

Answer: A parasite is an organism that lives off another organism called the host. The parasite often harms or kills its host. Examples of fungi that are parasitic in humans are those that cause ringworm and athlete’s foot.

5. What is symbiosis? Give an example of symbiosis.

Answer: Symbiosis is a relationship between two organisms that live together where at least one of the organisms benefits from the association. An example of symbiosis can be seen in lichen.

1. How are Fungi different from plant-like protists?

Answer: 1. Fungi cells lack chloroplasts; as a result, fungi are heterotrophs. The plant-like protists are green, have chloroplasts and are autotrophic (making their own food by photosynthesis).

2. How are Fungi important to soil health and maintenance?

Answer: 2. Fungi are important to soil health and maintenance because they decompose dead plant material, returning important nutrients to the soil.

3. How do the two organisms that make up lichen depend on one another?

Answer: 3. Lichen is a combination of a green alga (or blue-green bacteria) living inside a fungus. The alga or bacteria provide the fungus with food produced by photosynthesis. The fungus provides the alga or bacteria with a place to live and the moisture necessary for photosynthesis.

4. Why can’t Fungi make their own food?

Answer: 4. Fungi can’t make their own food because they are nongreen, lacking the photosynthetic pigment chlorophyll.

1. List the major characteristics of the kingdom Plantae.

Answer: Plantae are autotrophic and make their own food by photosynthesis. They have the green pigment chlorophyll. Green plants are multicellular and eukaryotic and can be classified into several phyla or divisions.

2. How do green plants obtain food?

Answer: Green plants have chlorophyll and can make their own food by photosynthesis. During photosynthesis, plants take in carbon dioxide and water from their environment, producing a sugar called glucose. Glucose serves as food for the plant.

3. What are the characteristics of Bryophytes?

Answer: Bryophytes are low-growing green plants that do not have vascular tissue for the transport of materials. Also, they do not have true roots, stems or leaves. Examples of Bryophytes are liverworts and mosses.

4. What are the characteristics of vascular plants?

Answer: Vascular plants have vascular tissue (for the transport of materials), true roots, stems, and leaves. As a result, they can grow tall. Examples of vascular plants are trees and shrubs.

5. How can we tell if a plant is a conifer?

Answer: Most conifers have needle-like leaves, are evergreen, and reproduce from seeds found in cones.

1. How are green plants different from fungi?

Answer: 1. Green plants have chlorophyll, are autotrophic, and make their own food by photosynthesis. Fungi cells lack chloroplasts, are heterotrophic, and obtain their food from decaying vegetation.

2. Why can’t Bryophytes grow as tall as vascular plants?

Answer: 2. Bryophytes do not have the vascular tissue needed to transport materials upward in a plant. As a result, they can’t grow as tall as vascular plants.

3. How is reproduction in Coniferophyta different from Anthophyta?

Answer: 3. Coniferophyta reproduce from seeds found in cones. Anthophyta reproduce from seeds found inside fruit.

4. Compare the seeds of a Monocot with the seeds of a Dicot.

Answer: 4. Monocots have one seed part (cotyledon) that cannot be split. Dicots have two seed parts (cotyledons) that can be split into two halves.

1. List the major characteristics of kingdom Animalia.

Answer: Animals are multicellular, heterotrophic organisms. Animals use locomotion to find food. Animal cells are eukaryotic. Some animals are classified as invertebrates; others are vertebrates.

2. How can we distinguish between the Porifera and the Cnidaria?

Answer: Porifera are sponges; they do not have a mouth but have pores that draw in water for cells to filter and absorb food. Sponges have two cell layers, and most are marine and sessile. Cnidaria are the coelenterates and include hydra, jellyfish, coral, and sea anemones. Cnidaria have two cell layers, a mouth for ingestion, and a hollow body cavity for digestion. They also have stinging cells, tentacles, and many are motile.

3. Define bilateral symmetry.

Answer: In bilateral symmetry, the right and left sides of the organism are similar.

Answer: Platyhelminthes are flatworms. Examples are planaria and tapeworms. Nematodes are roundworms. Examples are trichinella and hookworm. Annelida are segmented worms. Examples are the earthworm and sandworm.

5. What are the major characteristics of the Annelida?

Answer: Annelida are segmented worms and have a tube-within-a-tube body construction.

1. How are animals different from green plants?

Answer: 1. Animals are heterotrophic organisms that depend on locomotion to find food. Green plants have chlorophyll and can make their own food by photosynthesis. During photosynthesis, plants take in carbon dioxide and water from their environment—producing a sugar called glucose. Glucose serves as food for the plant.

2. Why is an octopus classified as a mollusk?

Answer: 2. Mollusks have soft bodies and a hard shell. In the case of the octopus, the shell is inside a soft body.

3. How are insects different from spiders?

Answer: 3. Insects are members of the class Insecta. Insects have three body parts: head, thorax, and abdomen. Insects also have three pairs of legs. Most have two pairs of wings, and many are capable of metamorphosis. Spiders are members of the class Arachnida. Spiders have two body parts (cephalothorax and abdomen), eight legs, and no wings.

4. What is metamorphosis?

Answer: 4. Metamorphosis is a complete change in the body structure of an organism from young to adult. The transformation of a caterpillar into a butterfly is an example of metamorphosis.

5. How is respiration in a crustacean different from respiration in an insect?

Answer: 5. Crustaceans use gills for breathing, and insects use tracheal tubes.

1. What is meant by cold blooded? Which classes of vertebrates are cold blooded?

Answer: In a cold-blooded animal, the body temperature of the organism is the same as that of the environment. Fishes are cold blooded. As the temperature of the water that a fish is swimming in changes, the body temperature of the fish changes accordingly. Other vertebrate classes that are cold blooded are amphibians and reptiles.

2. How are invertebrates different from vertebrates?

Answer: Invertebrates are animals without backbones; vertebrates are animals with backbones.

3. Why are turtles classified as reptiles and not fishes?

Answer: Although many turtles spend much of their lives in water, they have lungs for breathing and they return to land to reproduce. Fishes breathe through gills and are basically marine or fresh water organisms.

1. Why is a bat a mammal and not a bird?

Answer: 1. A bat is classified as a mammal because it has hair, and the females have mammary glands that can feed milk to their young. Although a bat can fly, it does not have feathers, which is a characteristic that is exclusive to birds.

2. How are fishes different from amphibians?

Answer: 2. Fishes have scales, fins, and gills for breathing. Amphibians have lungs as adults and lack fins and scales. Amphibians have the ability to perform metamorphosis, but fishes do not.

29. An organism that has hair, mammary glands and feeds milk to its young can be classified

as a: A. bird B. mammal C. reptile D. amphibian Answer: B

30. Why is a virus not classified into a kingdom?

A. Most biologists do not consider them living things. B. They are primitive cells. C. They can reproduce. D. Many cause disease in plants and animals. Answer: A

1. How is an atom different from an element?

Answer: An element is a substance that contains only one kind of atom. The element sulfur contains only sulfur atoms, iron contains only iron atoms and so on. The atom is the smallest part of an element that still retains all the properties of the element.

2. Define compound and give some examples of compounds.

Answer: A compound is a chemical combination of two or more kinds of atoms. In a compound, atoms of elements lose their original properties and take on the properties of the compound. Examples of compounds are water, salt, and methane.

3. When do we use symbols and formulas?

Answer: A symbol is an abbreviation for an element, and a formula is an abbreviation for a compound.

4. What is a chemical bond?

Answer: A chemical bond is the electron arrangement (or force) that holds atoms together. The two kinds of chemical bonds are the ionic bond and the covalent bond.

5. Look at the chemical formula for stearic acid: C17H35COOH. What kind of compound is stearic acid?

Answer: Stearic acid is an organic compound. Stearic acid contains carbon and hydrogen together; compounds of carbon and hydrogen are usually organic.

1. Name the elements found in all living things.

Answer: The elements that are found in all living things are hydrogen, oxygen, nitrogen, and carbon. Remember the pneumonic device HONC.

2.How many bonds can a carbon atom form?

Answer: Carbon forms four bonds when creating a compound.

3.Look at the structural formulas for ethane and propane in the preceding figures. What kind of compound are these?

Answer: Ethane and propane are organic compounds. Their structural formulas show that they contain carbon and hydrogen.

1. How is a chemical formula different from a structural formula?

1. A chemical formula shows the elements and the number of atoms for each element in a compound. A structural formula adds to this the arrangement of the atoms in the compound.

2. What does the line between C and H in a structural formula represent?

2. In a structural formula, the line between the carbon and hydrogen atoms represents a covalent bond, which is a pair of shared electrons.

1. What is the most abundant compound found in all living things? Why is this compound important?

Answer: Water, which is inorganic, is the most abundant compound found in all living things. Without water, life on earth could not exist because the cytoplasm of a cell contains mostly water. Most organisms are composed of 70%–95% water.

2. What elements are found in carbohydrates?

Answer: The elements found in carbohydrates are carbon, hydrogen, and oxygen. The suffix -ate indicates the presence of oxygen.

3. What is the ratio of hydrogen atoms to oxygen atoms in a carbohydrate?

Answer: The ratio of hydrogen atoms to oxygen atoms in a carbohydrate is 2:1.

4. Why are carbohydrates biologically important?

Answer: Carbohydrates are an important source of energy for organisms.

5. How are monosaccharides different from disaccharides?

Answer: Monosaccharides are simple (or single) sugars. When two monosaccharides are combined, we get a double sugar called a disaccharide.

1. What is dehydration synthesis?

1. Dehydration synthesis is the formation of a large molecule from two smaller molecules by the removal of water.

2. Explain how the maltose molecule is formed.

2. Maltose is a disaccharide that is formed by combining two glucose molecules via dehydration synthesis.

3. Explain how maltose can be broken down.

3. The maltose molecule can be broken down into two glucose molecules by adding water. This type of chemical reaction is called hydrolysis. Hydrolysis is the opposite of dehydration synthesis.

4. How are polysaccharides formed?

4. A polysaccharide consists of many glucose molecules combined. Polysaccharides can be formed by dehydration synthesis.

5. Why are starch and glycogen important molecules in living things?

5. Starch is a storage form of sugar in plants, and glycogen is a storage form of sugar in animals. It is much more efficient to store one molecule of starch than hundreds of glucose molecules. When a plant needs sugar for energy production, starch molecules can be broken down by hydrolysis.

1. Describe the structure of glycerol.

Answer: Glycerol is an alcohol that has a three-carbon chain. Each carbon has a hydroxyl group (OH-) attached to it.

2. Describe the structure of a fatty acid.

Answer: A fatty acid is an organic molecule with a long carbon chain that ends with a carboxyl group (COOH).

3. Give several examples of lipids.

Answer: Lipids are organic molecules that include fats, oils, and waxes.

4. Why are lipids biologically important?

Answer: Lipids are used for energy and, along with proteins, help form the membranes

of cells.

1. Describe the formation of a lipid.

1. Lipids are formed by dehydration synthesis. One glycerol molecule is combined with three fatty acid molecules.

2. How are lipids broken down?

2. Lipids are broken down by hydrolysis. One lipid molecule + three water molecules yield one glycerol molecule + three fatty acid molecules.

3. Both lipids and sugars provide energy. From your examination of their structural formulas,

can you discover which molecule is capable of providing the most energy?

3. A molecule of lipid can release more energy than a molecule of sugar. A careful examination of the structural formulas of the two molecules shows that the lipid molecule is larger than the sugar molecule. When broken down, the lipid releases the most energy.

1. What elements are found in proteins?

Answer: Carbon, hydrogen, oxygen, and nitrogen are the elements found in all proteins. Only proteins have the element nitrogen.

2. What are the building blocks of proteins?

Answer: Amino acids are the building blocks of proteins.

3. Give several examples of proteins and state their importance.

Answer: Hemoglobin—Aids in the transport of oxygen to the cells of an organism. Antibodies—Proteins in the blood that can help fight disease. Nucleoproteins—The DNA molecule is important for heredity and reproduction. RNA aids in protein synthesis. Hormones—Chemical messengers that aid in the life function of regulation. Enzymes—Organic catalysts that speed up the rate of chemical reactions.

4. What is a peptide bond?

Answer: A peptide bond is a carbon-nitrogen bond that holds two amino acid molecules together. The peptide bond is formed by dehydration synthesis.

1. Describe the formation of a protein.

. Proteins are formed by the dehydration synthesis of 40 or more amino acids. Many proteins are complex molecules containing millions of amino acids.

2. Where are proteins formed?

2. Protein synthesis takes place at the ribosome.

3. State the difference between a dipeptide and a protein.

3. A dipeptide is a compound of two amino acids combined by one peptide bond. A protein is the combination of 40 or more amino acids.

4. How are proteins broken down?

4. Proteins are broken down into amino acids by hydrolysis.

5. How many kinds of proteins can be formed from 20 different amino acids?

5.The number of different proteins that can be made is infinite. Think of each of the 20 different amino acids in the human body as a letter of the alphabet. The smallest word these letters form can have any combination of 40 letters, and many words can be millions of letters long. An infinite number of words can be produced. Now just imagine that each word is a protein! Of the infinite number of proteins possible, the human body has approximately 50,000 different proteins.

4. Which is a stronger acid, pH 3 or pH 5?

4. pH 3 is the stronger acid because it is further away from neutral on the acid side of the pH scale. The lower the acid pH number, the stronger the acid.

5. Which is a stronger base, pH 8 or pH 10?

5. pH 10 is a stronger base because it is further away from neutral on the base side of the pH scale. The higher the base pH number, the stronger the base.

6. Why is NaCl not an acid?

6. NaCl is not an acid because it does not produce the hydrogen ion (H+).

1. Why are enzymes important?

Answer: Enzymes speed up the rate of chemical reactions. Without enzymes, the chemical reactions that take place in an organism do not work, and the organism dies.

2. Define the term substrate.

Answer: The substrate is the substance that an enzyme works on. For example, in the formation of a lipid, the substrate is glycerol and three fatty acids.

3. What is the enzyme-substrate complex?

Answer: An enzyme-substrate complex forms when an enzyme combines with a substrate.

4. Explain what is meant by saying “enzyme action is specific.”

Answer: Only one kind of enzyme can be used for each type of chemical reaction. For example, maltase can be used to make or break down maltose; lipase can be used to make or break down a lipid. However, maltase cannot be used to make or break down a lipid, and lipase cannot be used to make or break down maltose.

5. What kind of molecule is kinase?

Answer: Kinase is an enzyme. All enzymes end in the suffix -ase. The ending on the name of a compound can be used to identify the type of compound. Compounds with names ending in -ose are sugars, compounds with names ending in -ol are alcohols, and most compounds with names ending in -ine are amino acids. Note that some amino acids have names that do not end in -ine, such as aspartic acid.

1. Explain the lock-and-key model of enzyme action.

1. The lock-and-key model of enzyme action is used to show that only one kind of enzyme can be used to speed up each type of chemical reaction, just as only one key can fit into a lock. An enzyme can be used to help make or break down a compound, and an enzyme is never used up. A key can be used to open or close a lock again and again. In organisms, the enzyme is the key, and the substrate is the lock.

2. Why can’t the enzyme protease speed up the formation of maltose from two glucose molecules?

Protease cannot speed up the formation of maltose from glucose because the active site of protease is not compatible with the shape of the glucose molecules, and therefore an enzyme-substrate complex cannot form. However, maltase can be used to make maltose, and protease can be used to make a protein. Enzyme action is specific: One enzyme is used for each type of chemical reaction, and it must be the correct enzyme!

3. How do temperature and pH affect the rate of enzyme action?

3. Very high and low temperatures distort the active site of an enzyme. As a result, the rate of enzyme action decreases. Very low or very high pH has a similar effect on the rate of enzyme action.

4. How do enzyme and substrate concentration affect the rate of enzyme action?

4. As more enzymes are added, enzyme action increases and eventually levels off when all the substrate is being worked on. As more substrate is added, enzyme action increases and eventually levels off when all the enzymes are being used.

5. Why does a high fever make a person feel sick?

5. When a person has a fever, the higher temperature distorts the active sites of enzymes in the body. As a result, the rate of many chemical reactions decreases, making a person feel sick.

1. What is the function of the cuticle? Why must it be transparent?

Answer: The cuticle is a thin, waxy layer that covers the upper epidermis of a leaf and prevents the loss of water. The cuticle must be transparent so that light can pass through to the photosynthetic cell layers of the leaf.

2. Which cell layers of the leaf are capable of photosynthesis?

Answer: The palisade and spongy mesophyll layers are capable of photosynthesis.

3. How is the upper epidermis of the leaf different from the lower epidermis?

Answer: The upper epidermis of many leaves has a waxy cuticle that the lower epidermis does not. The lower epidermis has guard cells and stomates, which are lacking in the upper epidermis.

4. Why are the vascular bundles of a leaf important?

Answer: The vascular bundles form the transportation network of the leaf, stem, and root. The phloem cells carry sugar and starch down to the roots for storage. The xylem cells carry water and minerals up from the roots.

5. What is the function of the guard cells?

Answer: Guard cells control the opening and closing of the stomates. During the day the guard cells produce sugar by photosynthesis, causing their walls to curve inward and away from each other and creating a space between the cells called a stomate. At night the process is reversed, and the stomate closes.

1. Why is the leaf an important plant structure?

1. The leaves of plants are important because they are the sites for photosynthesis in plants. During photosynthesis, plants produce glucose that they and other organisms depend on for food. Many organisms use oxygen produced during photosynthesis in the life process of respiration.

2. Which cell layer of the leaf performs the most photosynthesis?

The palisade layer performs the most photosynthesis. Look at the diagram of the cross section of the leaf:The palisade layer cells are closer to the sun. Many palisade layer cells are packed tightly together. Palisade cells are large cells and contain many chloroplasts. Spongy mesophyll layer cells don’t perform as much photosynthesis as palisade layer cells. Spongy mesophyll cells are further from the sun, fewer in number, smaller, and don’t have as many chloroplasts.

3. Why must desert plants have a thick, waxy cuticle?

Desert plants must have a thick, waxy cuticle to prevent the loss of water.

4. What are the functions of the stomates?

4. The stomates of a leaf function in photosynthesis, respiration, transpiration, excretion, and evaporation. Photosynthesis—The stomates allow carbon dioxide into the leaf. Carbon dioxide and water combine to form glucose and oxygen. Respiration—The stomates allow oxygen into the leaf. Oxygen is used to release the energy stored in glucose.Transpiration—Water is lost through the stomates. Excretion—Oxygen is a waste product of photosynthesis that can exit the leaf through the stomate. Carbon dioxide is a waste product of respiration that also exits the leaf through the stomate. Evaporation—The change of a liquid into a gas.

5. Why must plants have both carbon dioxide and oxygen?

Plants require carbon dioxide for photosynthesis and oxygen for respiration. Plants are capable of both processes. Animals perform only respiration.

3. Why is chlorophyll needed for photosynthesis?

Answer: Chlorophyll traps light energy that is used to split water molecules.

4. Why is the green wavelength of light of little use in photosynthesis?

Answer: Green is the worst wavelength of light for photosynthesis because the leaf reflects rather than absorbs this wavelength, making it unavailable to the plant as a source of energy.

5. What is a coenzyme?

Answer: A coenzyme is a molecule that can transfer hydrogen and electrons from one reaction to another. In photosynthesis, the coenzyme NADP transfers hydrogen and electrons from light to dark reactions. In humans, many vitamins function as coenzymes.

1. What is the function of the stem?

Answer: The stem supports the leaves of the plant while serving as a pathway for the transport of water and minerals up from the roots and sugars and starches down from the leaves.

2. How are monocot stems different from dicot stems?

Answer: Monocots are nonwoody (herbaceous) plants with vascular bundles that are scattered throughout the stem. Monocot vascular bundles lack cambium cells, and most are annuals, living for only one growing season. Dicots are woody plants with vascular bundles found directly behind the bark. The vascular bundles of dicots contain phloem, cambium, and xylem. Dicots are perennial plants.

3. How are annual rings formed?

Answer: In the winter, cold temperatures kill phloem and xylem cells, producing a ring of dead cells called an annual ring.

4. What is translocation?

Answer: Translocation is the movement of food through a plant.

1. Compare phloem and xylem in terms of the direction in which each transports materials. What materials does each type of cell carry?

1. Phloem cells are specialized for downward transport, carrying sugars and starches to the roots. Xylem cells are specialized for upward transport, carrying water and minerals up to the leaves.

2. Why are cambium cells important?

2. Cambium cells are important because they are meristematic cells and are capable of producing phloem and xylem.

3. Why must a stem have lenticels?

3. A stem must have lenticels for respiration. These small openings in the stem allow oxygen in and carbon dioxide out. The living cells of the vascular bundle use the oxygen for energy production.

4. How does girdling kill a tree?

4. Girdling breaks the continuity of the vascular bundles. Water is not able to move up the stem, and food is not able to move down. As a result, the plant eventually dies.

1. What are the functions of the root?

Answer: The root anchors the plant to the ground and supports the stem. Roots absorb water and minerals, sending these materials up through the stem to the leaves. Also, roots serve as a major storage site of starch.

2. Which cells in the root are used for storage?

Answer: The cortex cells of the root are used for storage.

3. Name the process by which water can enter a root hair cell.

Answer: Osmosis is the process by which water can enter a root hair cell. In osmosis, water moves from areas of high concentration to areas of low concentration. If you missed this question, review molecular transport in Chapter 2.

1. How are epidermis cells different in structure and function from root hair cells?

1. Epidermis cells are the outer layer of cells in a root. Epidermis cells are small and round and function in the absorption of water and minerals from the soil. Root hair cells are elongated cells on the outside of the root with a large surface area that is specialized for the absorption of water and minerals. The large surface area of root hair cells allows them to absorb more water than the epidermis cells.

2. Why does the plant store food in the roots as starch rather than as glucose?

2. Starch is a polysaccharide formed from many molecules of glucose combined. It is more efficient to store one molecule of starch as opposed to several hundred molecules of glucose.

3. Why don’t root cells need chloroplasts?

3. Chloroplasts contain the chlorophyll molecule, which is used to trap light energy needed for photosynthesis. Because roots are underground and not exposed to light, it is pointless for them to have chloroplasts.

4. How are meristematic cells in the root important?

4. Meristematic cells are reproductive cells. The meristematic cells of the root are responsible for root growth deeper into the soil.

1. Where does the digestion of starch, protein, and lipids begin and end?

Answer: Starch digestion begins in the mouth, protein digestion begins in the stomach, and lipid digestion begins in the small intestines. All digestion is completed in the small intestines.

2. What is peristalsis?

Answer: Peristalsis is a series of involuntary muscle contractions of the esophagus that forces food into the stomach.

3. Where does most digestion take place?

Answer: Most digestion takes place in the small intestines, and all digestion is completed there.

4. What is the role of the appendix in the digestive process?

Answer: The appendix is a vestigial organ and does nothing for human digestion. At some point in human evolutionary history, it probably did have a digestive function.

5. How is mechanical digestion different from chemical digestion?

Answer: Mechanical digestion is a physical process that breaks food down into smaller particles, but the type of food remains the same. Chemical digestion breaks down carbohydrates into sugars, proteins into amino acids, and lipids into glycerol and fatty acids.

1. How do the liver and pancreas aid the process of digestion?

1. The liver produces bile, which emulsifies fats. The pancreas produces pancreatic fluid that contains several enzymes, which help break down carbohydrates, proteins, and lipids. The pancreatic fluid also contains bicarbonate, which neutralizes the acid from the stomach.

2. Why is mechanical digestion important?

2. Mechanical digestion is important because it increases the surface area of food, making chemical digestion more efficient.

3. Why is hydrochloric acid important for digestion?

3. Hydrochloric acid is important because it activates pepsinogen, forming pepsin (a gastric protease), which begins the breakdown of proteins into small polypeptides and amino acids. Pepsin requires acidic conditions to function.

4. What are the end products of digestion?

4. The end products of digestion are sugars, amino acids, glycerol, and fatty acids.

5. How do the end products of digestion get to the cells of the body?

5. The end products of digestion enter the blood from the villi of the small intestines.The circulatory system transports these food molecules to all cells of the body.

1. What is the structure and function of the heart?

Answer: The heart pumps blood and helps maintain blood pressure. Actually, the heart is a dual pump with two sides. The right atrium receives blood from the body, and the right ventricle pumps blood to the lungs. The left atrium receives blood from the lungs, and the left ventricle pumps blood out to the organs of the body.

2. Why is the human transport system called a circulatory system?

Answer: In humans, blood flows clockwise in a circle beginning and ending with the heart. It is a closed circulatory system because blood never leaves the blood vessels.

3. Name the different blood vessels and state their structure and function.

Answer: The human blood vessels are arteries, veins, and capillaries. Arteries have thick muscular walls that pulse and carry blood away from the heart to the organs. Veins have thin muscular walls that contain valves and carry blood back to the heart. Capillaries are one cell in diameter and connect arteries to veins.

4. What is the structure and function of each of the following blood components: plasma, red blood cells, white blood cells, and platelets?

Answer: Plasma is the straw-colored liquid part of the blood and makes up about 55% of the blood. Plasma consists mostly of water and proteins. Plasma carries the end products of digestion to the cells, transports urea wastes from the cells, and transports antibodies, hormones, and other proteins. Red blood cells have the iron-containing hemoglobin molecule that helps transport oxygen to the cells and carbon dioxide from the cells. White blood cells help the body fight disease by destroying bacteria and other foreign substances. Platelets are cell fragments that interact with fibrinogen and help the blood to clot.

1. Which blood vessels carry the most deoxygenated blood?

1. The two pulmonary arteries carry the most deoxygenated blood from the right ventricle to the lungs. Deoxygenated blood is low in oxygen but high in carbon dioxide. In the lungs, an exchange of gases takes place; the red blood cells lose carbon dioxide and pick up oxygen. Oxygenated blood returns to the heart via the four pulmonary veins. The left ventricle pumps the oxygenated blood to all parts of the body. In general, arteries carry oxygenated blood, and veins carry deoxygenated blood. The pulmonary arteries and pulmonary veins are the exceptions.

2. How does oxygen enter red blood cells?

2. In the lungs, oxygen enters the red blood cells by diffusion. The concentration of oxygen in the lungs is much higher than in the red blood cells, and the oxygen molecules move from areas of high concentration to areas of low concentration.

3. How is the backward flow of blood in the circulatory system prevented?

3. The backward flow of blood in the circulatory system is prevented by the pumping action of the heart, which helps to keep the blood flowing in a forward direction. Valves in the heart prevent the backward flow of blood in the heart, and valves in the veins prevent the backward flow of blood in those blood vessels.

4. Why must the left ventricle have the thickest walls of the heart?

4. The left ventricle has the thickest walls of the heart because it must pump blood throughout the entire body.

5. Outline the pathway of blood flow from the right toe to the heart and back to the right toe.

5. Capillaries in the right toe → small veins in the toe → large vein in the right leg → inferior vena cava → right atrium → right ventricle → pulmonary arteries → lungs → left atrium → left ventricle → aorta → large artery in the right leg → small arteries in the right toe → capillaries in the toe.

1. How does oxygen enter the body?

Answer: Oxygen enters the body through the nose or the mouth.

2. Why does the trachea have rings of cartilage?

Answer: The rings of cartilage in the trachea are needed to keep the trachea constantly open. If the trachea collapses, air containing oxygen is not able to enter the body, and this could cause death.

3. How is food kept out of the trachea?

Answer: When a person swallows, a small flap called the epiglottis covers the trachea and prevents food from entering, keeping the person from choking to death.

2. The alveoli are air sacs found in the lungs and surrounded by capillaries. Oxygen from the

alveoli diffuses into the capillaries.

3. How does oxygen enter a red blood cell?

3. Oxygen enters a red blood cell by the process of diffusion. Diffusion is the movement of molecules from areas of high concentration to areas of low concentration. In the lungs, capillaries that surround the alveoli have a high concentration of oxygen, and red blood cells have a low concentration of oxygen. As a result, oxygen diffuses across the moist membranes of red blood cells to enter these cells.

4. What is the role of the diaphragm in respiration?

4. The diaphragm forces air into and out of the lungs. The diaphragm is a muscle located under the lungs. As the diaphragm moves up, air is pushed out of the lungs. As the diaphragm moves down, air is pulled into the lungs.

5. What factor determines how quickly humans breathe?

5. The level of CO2 in the blood determines the rate of respiration. The higher the CO2 level in the blood, the faster the rate of respiration.

1. Which waste products do the kidneys remove?

Answer: The kidneys remove urea, water, and salt from the blood. The resulting mixture is known as urine.

2. What is the role of each of the following structures in the urinary system: ureter, urinary bladder, and urethra?

Answer: The ureter is a tube that carries urine from the renal pelvis to the urinary bladder. The urinary bladder is a temporary storage site for urine. The urethra is a tube that carries urine from the urinary bladder to the outside of the body.

3. Outline the pathway of blood flow from the heart to the kidneys and back to the heart.

2. Urea is formed in the liver by the process of deamination. Amino acids lose their amino group to form ammonia, which is converted chemically into urea.

3. How do carbon dioxide and water get from the blood into the alveoli?

3. Carbon dioxide enters the alveoli by diffusion, and water enters by osmosis. Both of these molecules are moving from an area of high concentration in the capillaries that surround the alveoli to an area of low concentration inside the alveoli. Passive transport is the movement of molecules from areas of high concentration to areas of low concentration. Diffusion is the movement of any molecule except water. Osmosis is the movement of the water molecule.

4. What process produces the waste products removed by the lungs?

4. Cellular respiration produces the carbon dioxide and water that is removed by the lungs.

1. What are the functions of the skin?

Answer: The skin can function as an organ of excretion by removing sweat (water, urea, and salt) from the body. The skin also removes heat. The skin is the body’s first line of defense against disease. As long as the skin is intact, it acts as a barrier against harmful organisms such as bacteria.

2. Describe the structure and function of a sweat gland.

Answer: Sweat glands are coiled tubes with a duct that extends to the surface forming an opening called a pore through which water, urea, and salt wastes can exit.

1. How does the skin help maintain temperature homeostasis?

1. Heat is lost by radiation to the atmosphere when blood flows through dilated (widened) capillaries near the skin’s surface. In cold weather, the capillaries constrict (narrow) and less blood flows through the skin, conserving heat. Humans are warm blooded and must maintain a constant body temperature of approximately 37°C.

2. What happens if the body cannot remove excess heat?

2. If excess heat is not removed, body temperature goes up. The active sites of enzymes become distorted, and important chemical reactions in the body slow down and stop. This can cause sickness and possibly death.

3. How are wastes removed from the skin different from those removed by the kidneys?

3. Both the skin and the kidneys remove urea, water, and salt. However, unlike the kidneys, the skin removes very little urea. Sweat removed by the skin is about 99% water. The skin plays a major role in regulating the body’s temperature by either removing or conserving heat. Almost no heat is lost by the removal of wastes from the kidneys.

1. Why must some organisms be capable of locomotion?

Answer: Locomotion is the ability of an organism to move from one place to another to obtain food, find a mate, and avoid predators.

2. How is an endoskeleton different from an exoskeleton?

Answer: An endoskeleton is one where the bones and cartilage are found inside the body. An exoskeleton is found outside the body and is made of a hard, shell-like substance called chitin.

3. What is a joint?

Answer: A joint is where two bones meet.

4. How are bones connected to each other?

Answer: Ligaments connect bones to each other.

1. Describe the structure and function of skeletal muscle.

1. Skeletal muscle is made of cells that have combined to form fibers called striations. The function of these muscles is to move the bones during locomotion.

2. How are skeletal muscles connected to bones?

2. Skeletal muscles are connected to bones by tendons.

3. How do muscles work together in pairs to achieve locomotion?

3. Muscles of the endoskeleton work together in pairs called flexors and extensors. Flexors move bones toward the body, and extensors move bones away from the body. As the bones move, so does the person.

4. How are voluntary muscles different from involuntary muscles?

4. Voluntary muscles are muscles that are consciously controlled. Skeletal muscles are an example of voluntary muscles; decisions can be made about when to use them. Involuntary muscles are muscles that are not consciously controlled. Smooth muscle and cardiac muscle are examples of involuntary muscles.

1. Which systems in the body are responsible for carrying out the life function of regulation?

Answer: The nervous system and the endocrine system, working together, carry out the life function of regulation.

2. Distinguish between a stimulus and a response.

Answer: A stimulus is a change in the environment of an organism. A response is the reaction of an organism to a stimulus.

3. How are receptors different from effectors?

Answer: Receptors are organs in the body capable of detecting a stimulus. The effectors are the organs that carry out the response. The receptors are the five sensory organs of the body: eyes, ears, nose, tongue, and skin. The effectors are the muscles and glands of the body. The skeletal muscles help with locomotion, and the endocrine glands help regulate various organ systems.

1. How does the life function of regulation help a person survive?

1. The life function of regulation helps a person adapt to changes in the environment. The reaction of the person is the response. The ability to respond to environmental change enables the individual to maintain homeostasis and survive. For example, a person walking down a street sees a large box and walks around it. The box was the stimulus, and walking around the box was the response. However, if the person didn’t see the box and tripped over it, he might be injured or break his neck and die.

2. What are the characteristics of nervous system responses?

2. Nervous system responses are fast, have a short duration and are limited in scope. For example, if a person touches a hot object, his hand is removed in a fraction of a second. The response is over quickly and is limited to just the person’s hand.

3. What is the role of the nerve cells of the body?

3. The nerve cells are the basic unit of structure and function in the nervous system. The nerve cells act as lines of communication between the various parts of the body. Nerve cells act as a link between the receptors and the brain or spinal cord. Nerve cells keep the brain and spinal cord in contact with the effectors of the body. Also, the brain is made of millions of nerve cells.

4. Describe the role of the brain?

4. The brain is the processing center of the body. The brain receives information from the receptors, interprets this information, and signals an effector to carry out an appropriate response. The brain is not a receptor organ. Without receiving information from a receptor, the brain doesn’t know anything.

5. What is the effect on the body if the nerve cells from the spinal cord to the effectors are damaged?

5. If the nerve cells from the spinal cord to the effectors are damaged, a person might be paralyzed in part of his body. The nerve cells from the spinal cord signal the effectors to carry out an appropriate response. Damaged nerve cells break the line of communication to the effectors, preventing them from responding.

1. What is the relationship between neurons, nerve cells, and nerves?

Answer: Neurons and nerve cells are different names for the same structure. A nerve is a bundle of axons surrounded by connective tissue.

2. What are the parts of the cyton and their function?

Answer: The parts of the cyton are: Nucleus: Controls the nerve cell and functions in reproduction Cytoplasm: The site of the organelles and chemical reactions Dendrites: Detect stimuli

3. Describe the role of the axon.

Answer: The axon connects the cyton to the terminal branches and carries the nerve impulse from the cyton to the terminal branches.

1. Describe the synapse.

1. The synapse is a space between the terminal branches of one neuron and the dendrites of the next neuron.

2. How does the nerve impulse get from one nerve cell to the next?

2. Neurotransmitters such as acetylcholine are chemicals produced by the terminal branches of a neuron that are secreted into the synapse. When they contact the dendrites of the next nerve cell, a nerve impulse begins in that nerve cell.

3. Describe the nerve impulse.

3. A nerve impulse is electrical and chemical, electrical in the nerve cell and chemical in the synapse between nerve cells. Inside the nerve cell, the nerve impulse is a depolarization wave. The axon of a resting nerve cell is positively charged on the outside and negatively charged on the inside; as an impulse goes down the axon, the outside becomes positively charged, and the inside becomes negatively charged. Between nerve cells, chemicals called neurotransmitters transmit the nerve impulse to the next nerve cell.

4. In which direction do nerve impulses travel?

4. Nerve impulses always travel from the cyton through the axon to the terminal branches.

5. Why is cholinesterase important?

5. Cholinesterase is important because it is the enzyme that breaks down acetylcholine in the synapse so that the same message does not keep repeating itself. If acetylcholine remains in the synapse, the dendrites of the next neuron are continuously stimulated. Cholinesterase breaks down acetylcholine to prevent this from happening. After cholinesterase does its work, it breaks down so that in the future, acetylcholine can again be produced in the synapse.

1. What is the role of each of the following neurons: sensory neuron, interneuron, and motor neuron?

Answer: The sensory neuron in a receptor detects the stimulus and transmits the nerve impulse to the interneuron. The interneuron is located in the spinal cord and receives the nerve impulse from the sensory neuron and relays the impulse to the motor neuron. The motor neuron transmits the impulse to an effector to carry out the response.

2. Why is the reflex arc important?

Answer: A reflex is an automatic, involuntary, unlearned response to a stimulus. The reflex arc is a great way to respond to a potentially harmful situation such as coming into contact with a sharp object or a flame, where a fast response is necessary to avoid injury.

3. Identify the parts of the brain and their function.

Answer: The brain has three major parts. The cerebrum is responsible for interpreting information received from the receptors. This is the conscious part of the brain and controls voluntary activities, judgment, and memory. The cerebellum controls coordination and balance. The medulla controls involuntary body activities such as breathing, heartbeat, digestion, blinking, and sneezing.

1. Why is it important that the brain not be involved in a simple reflex?

1. A simple reflex must be a fast, immediate, and automatic response to a stimulus for a person to avoid injury. The brain takes too long to evaluate information by thinking and processing. By the time the brain has finished doing its job, the person is probably injured. Consider the following example: A person accidentally touches a hot object. If the sensory neuron transmitted this information to the brain, the brain might start thinking along these lines, “The object is hot. How hot is it? Is it so hot that the hand must be removed now? Can the hand be removed later? How quickly should the hand be removed?” By this time the person’s hand might be severely burned. The simple reflex takes the thinking out of the response and gives a fast result!

2. Which part of the human brain is the largest?

2. The cerebrum is the largest part of the brain and controls the five senses, judgment, memory, voluntary activities, and much more.

3. Describe the function of the spinal cord.

3. The spinal cord plays a central role in the reflex arc, helping to control simple reflex actions when fast responses are needed.

4. Why is the cerebellum in squirrels large compared to their cerebrum? In humans, the cerebellum is small compared to the cerebrum.

4. A squirrel has the ability to walk on the branch of a tree and to jump from limb to limb without falling. Squirrels have a terrific sense of balance and coordination as a result of a large cerebellum in comparison to the size of their cerebrum. However, squirrels are not known for their thinking abilities.

5. Why is it important that the cerebrum not have control over respiratory activities?

5. Respiration is an activity that goes on all the time in humans. If the cerebrum controlled the process of respiration, little time would be left over for thinking. The cerebrum would be too concerned with when to breathe in, when to exhale, and so on. This is why the medulla controls activities that there isn’t time to think about, such as respiration and digestion.

1. How are endocrine glands different from exocrine glands?

Answer: Endocrine glands are ductless glands whose secretions (hormones) reach their target by traveling through the blood. Exocrine glands have ducts through which their secretions travel to reach their target.

2. What are hormones?

Answer: Hormones are chemical messengers produced by endocrine glands. Hormones signal other organs of the body to perform a variety of functions.

3. How do hormones reach their target?

Answer: Hormones reach their target by traveling through the blood. Endocrine glands do not have ducts that connect them to their target.

1. Describe the mechanism of hormone action.

1. The pituitary gland produces a stimulating hormone (SH) that travels through the blood to an endocrine gland. The endocrine gland detects the SH and produces its own hormone to reach a target. When the pituitary gland detects the endocrine gland’s hormone, the production of SH is stopped.

2. What is feedback and why is it important?

2. In the endocrine system feedback is important because it shuts down an endocrine pathway after the target organ has been signaled.

3. How is the nervous system similar to the endocrine system?

3. The nervous system and the endocrine system are similar in that they both play a major role in maintaining homeostasis, and both secrete chemical messengers. The nervous system produces neurotransmitters, and the endocrine system produces hormones.

4. How is the nervous system different from the endocrine system?

4. Three differences exist between the nervous system and the endocrine system: Nerve impulses travel through neurons; hormones travel through the blood. Nerve responses are faster than endocrine responses. Nerve responses are of shorter duration than endocrine responses.

1. Why is the pituitary gland called the master gland?

Answer: The pituitary gland is called the master gland because it produces hormones that control the other endocrine glands. For example, stimulating hormones (SHs) target other endocrine glands to produce their hormones.

2. What organ controls the pituitary gland?

Answer: The hypothalamus of the brain produces hormones that control the pituitary gland and has nerve fibers that extend into this gland. The hypothalamus is the organ that ties the nervous system to the endocrine system.

3. What is the function of the thyroid gland?

Answer: The thyroid gland produces the hormone thyroxin. Thyroxin controls the rate of metabolism in most cells of the body, along with physical and mental development.

4. Why is adrenalin called the body’s emergency hormone?

Answer: Adrenalin is called the body’s emergency hormone because, in an emergency, adrenalin can signal the liver to release sugar into the blood for use by the muscles to produce energy. Adrenalin can increase the breathing rate, heartbeat, blood pressure, and blood clotting, preparing a person for fight or flight.

5. Identify the hormones produced by the gonads and discuss their function.

Answer: The ovaries of a female produce the hormones estrogen and progesterone. Estrogen is responsible for female secondary sex characteristics. Progesterone is a hormone that helps maintain the lining of the uterus. Estrogen and progesterone function

1. Explain how blood sugar levels in the body are regulated.

1. Insulin and glucagon regulate blood-sugar levels. Insulin targets the liver and instructs it to remove sugar from the blood and to produce glycogen (animal starch). Glucagon targets the liver, causing it to break down glycogen into sugar, which is released into the blood.

2. How do the parathyroid glands regulate the level of calcium in the blood?

2. The parathyroid glands regulate the level of calcium in the blood by producing the parathyroid hormone, which targets the bones to release calcium. Bones are mostly calcium and can act like a bank for this mineral.

3. Which hormones are produced by the adrenal cortex, and what is their function?

3. Cortisone, cortisol, and aldosterone are produced by the adrenal cortex. Cortisone and cortisol are anti-inflammatories and have antiallergic effects. Cortisone can treat skin diseases and help manage stress. Aldosterone regulates the level of salt in the blood and helps maintain the body’s electrolyte balance.

4. Why is the pancreas considered both an exocrine and endocrine gland?

4. The pancreas produces pancreatic fluid, which enters the small intestines through a duct, acting as an exocrine gland. The pancreas contains the Islets of Langerhans cells that produce the hormones insulin and glucagon, which reach their targets by traveling through the blood. In this way, the pancreas functions as an endocrine gland (or ductless gland).

5. How should a person with hypoglycemia be treated?

5. A person with hypoglycemia has a low blood-sugar level. It might be tempting to treat this condition by simply telling the person to eat foods with sugar. This is a mistake that could result in death. The mere symptoms of a disease should not be treated; the cause of a disease should be. When an individual with hypoglycemia eats foods with sugar, the Islets of Langerhans respond by oversecreting insulin, lowering the sugar level further. A person with hypoglycemia should be put on a low-carbohydrate diet to prevent the oversecretion of insulin and the lowering of sugar levels that follow.

1. How is extracellular digestion different from intracellular digestion?

Answer: Extracellular digestion takes place outside the cells of an organism in an organ or organ system specialized for this purpose. Intracellular digestion takes place inside cells in organelles called food vacuoles. Most organisms have both extra- and intracellular digestion. The exception is unicellular organisms, which have only intracellular digestion.

2. How do animal-like protists excrete carbon dioxide and ammonia?

Answer: Carbon dioxide and ammonia are excreted by diffusion through the cell membrane into the surrounding water.

3. Where does digestion in animal-like protists take place?

Answer: Animal-like protists have food vacuoles for digestion.

1. Why do we study animal-like protists?

1. Animal-like protists are one-celled organisms that carry out their life functions in a manner typical of individual cells. They give us a better understanding of the functioning of individual cells in humans. For example, the life functions of human white blood cells called phagocytes are similar to those of amoeba.1. Animal-like protists are one-celled organisms that carry out their life functions in a manner typical of individual cells. They give us a better understanding of the functioning of individual cells in humans. For example, the life functions of human white blood cells called phagocytes are similar to those of amoeba.

2. How do the pseudopods of amoeba help with locomotion and nutrition?

2. The pseudopods of amoeba are false feet, which are used for locomotion and to capture food. The amoeba is like a blob that is constantly changing shape as its pseudopods move about. The amoeba uses its pseudopods to engulf food by a process called phagocytosis.

3. How do animal-like protists maintain water balance?

3. Animal-like protists live in water. As a result, water is constantly entering by osmosis. If water is not removed, the organism would swell and eventually explode. The contractile vacuoles of animal-like protists are organelles that squeeze excess water out by active transport.

4. Which food nutrient results in the production of ammonia as a waste product?

4. Proteins are the only nutrients in food that contain the element nitrogen. Ammonia is a nitrogenous waste that is produced as a result of protein digestion.

5. Why don’t the amoeba and paramecium need a transport system?

5. The amoeba and paramecium do not need a transport system because they are unicellular and in direct contact with their environment. Materials circulate within these organisms by the movement of the cytoplasm.

1. Describe the digestive system of a hydra.

Answer: The hydra has a two-way digestive system. Food enters through the mouth, and undigested food can exit from the mouth.

2. What wastes products are produced by a hydra?

Answer: A hydra can produce carbon dioxide and ammonia as waste products.

3. How does a hydra excrete wastes?

Answer: Carbon dioxide and ammonia are excreted by diffusion through the cell membrane of the hydra’s ectoderm cells into the surrounding water. The endoderm cells excrete these wastes into the water of the digestive cavity.

What kinds of digestion take place inside a hydra?

1. The hydra has extracellular digestion that takes place in the digestive cavity and intracellular digestion that takes place in the food vacuoles of the ectoderm and endoderm cells.

Why doesn’t a hydra need a transport system?

2. A hydra does not need a transport system because all its cells are in contact with its watery environment. The endoderm cells are in contact with water in the digestive cavity, and the ectoderm cells are in contact with the surrounding water.

How can a hydra move from one place to another?

3. A hydra is basically sessile. However, it can glide on its base and somersault. A hydra can move long distances by allowing water currents to carry it to a new location.

Why do all the tentacles of a hydra move even though only one is touched?

4. The hydra has a nerve net but does not have a brain or nerve cord to control its responses.

1. Describe the digestive system of an earthworm.

Answer: The earthworm has a one-way digestive system. The pharynx sucks in food from the mouth to the esophagus, where peristalsis forces the food into the crop. Food is stored in the crop and pushed into the gizzard for mechanical digestion. From the gizzard, food enters the intestines where chemical digestion occurs. From the intestines, digested food enters the blood, and waste leaves through the anus.

2. How does digested food get into the cells of the earthworm?

Answer: In earthworms, digested food enters the blood from the intestines. The capillaries from dorsal and ventral blood vessels distribute the digested food to the cells.

3. What waste products does the earthworm produce?

Answer: Earthworms produce carbon dioxide and water as waste products from respiration. They produce ammonia and urea as nitrogen wastes.

1. What kinds of digestion take place inside an earthworm?

1. The earthworm has extracellular digestion that takes place in the digestive system and intracellular digestion that takes place in the cells of the organs.

2. Describe the circulatory system of an earthworm.

2. The earthworm has a closed circulatory system, dorsal and ventral blood vessels surrounded by five aortic arches (hearts) that pump blood. Capillaries from the major blood vessels to the organs supply food and oxygen.

3. How can the earthworm move from one place to another?

3. The segments of the earthworm have muscles and four pairs of bristles (called setae) that grab the soil and allow the worm to dig.

4. Describe the nervous system of an earthworm.

4. The earthworm has a primitive brain that is composed of two ganglia connected to a ventral nerve cord. Together, the ganglia and the nerve cord coordinate the activities of the worm.

5. How does oxygen get into the cells of the earthworm?

5. Oxygen in the air diffuses through the moist skin of the earthworm into capillaries, which carry the oxygen to the two major blood vessels.

1. Describe the digestive system of a grasshopper.

Answer: The grasshopper has a one-way digestive system. The grasshopper has a mouth for the mechanical digestion of food. From the mouth, food enters the esophagus and moves into the crop for storage. Food in the crop enters the gizzard (where mechanical digestion takes place) and then moves into the stomach (where chemical digestion occurs). From the stomach, digested food enters the blood, and waste enters the large intestines, moves to the small intestines, and exits through the anus.

2. How does digested food get into the cells of the grasshopper?

Answer: From the stomach, digested food enters the blood, and the dorsal blood vessel sprays the blood over the organs.

3. What wastes products does the grasshopper produce?

Answer: Carbon dioxide from the cells diffuses into the tracheal tubes and exits through the spiracles. Uric acid is a solid, nitrogenous waste that exits through the anus.

1. What kinds of digestion take place inside grasshoppers?

1. The grasshopper has extracellular digestion that takes place in the digestive system and intracellular digestion that takes place in the cells of the organs.

2. Describe the circulatory system of a grasshopper.

2. The grasshopper has an open circulatory system with a dorsal blood vessel that can pump blood. The blood sprays out of the dorsal blood vessel to bathe the organs, supplying food to the cells.

3. How can the grasshopper move from one place to another?

3. Grasshoppers can walk and jump because they have three pairs of legs. Grasshoppers can fly because they have two pairs of wings.

4. Describe the nervous system of a grasshopper.

4. The grasshopper has a brain that consists of two large, combined ganglia that are attached to two ventral nerve cords. The brain and nerve cords coordinate the activities of the grasshopper.

5. Which digestive organs are found in insects but are not found in humans?

5. The crop and gizzard are digestive organs found in insects but not in humans.

1. How is asexual reproduction different from sexual reproduction?

Answer: Asexual reproduction is the formation of a new individual from one parent. Sexual reproduction is the formation of a new individual from two parents.

2. What kinds of organisms reproduce asexually?

Answer: Unicellular organisms such as amoeba, paramecia and yeast reproduce asexually. Some multicellular organisms such as molds and green plants reproduce asexually to form new individuals.

3. What happens to the parent cell when asexual reproduction is complete?

Answer: When the parent cell reproduces asexually, it does not exist anymore. Two daughter cells form from the parent, and they are identical to each other.

4. What are the advantages and disadvantages of asexual reproduction?

Answer: The advantages of asexual reproduction are that only one parent is required, and all the offspring are identical to the parent. The disadvantage is that no variety exists among the offspring.

1. Why must multicellular organisms be capable of asexual reproduction?

1. Multicellular organisms perform asexual reproduction to produce new cells for growth and to replace cells in the organism that have died.

2. Describe the events that occur during asexual reproduction.

2. During asexual reproduction, the cytoplasm divides equally; the chromosomes replicate and are distributed equally to each daughter cell.

3. How can a cell that has 10 chromosomes produce two daughter cells, each with 10 chromosomes?

3. During asexual reproduction, each chromosome replicates. If the parent cell has 10 chromosomes, after replication it has 20. When the cytoplasm divides, these 20 chromosomes are distributed equally so that each daughter cell has 10 chromosomes.

4. A human liver cell with 46 chromosomes reproduces asexually. How many chromosomes does each daughter cell have?

4. Each daughter cell has 46 chromosomes. The species number of chromosomes remains the same from one generation to the next.

5. Why must the chromosome number of an organism be the same from one generation to the next?

5. Chromosomes contain the hereditary information of a cell. If a daughter cell was produced with missing chromosomes, this error could result in the death of the cell because the functions controlled by that chromosome would not be available. For example, suppose the chromosome with the information needed to produce digestive enzymes was missing; the cell would not have the enzymes needed to digest food and would die.

1. Describe the process of binary fission.

Answer: An organism that reproduces by binary fission has equal division of the cytoplasm and equal distribution of the nuclear material to form two identical daughter cells.

2. What parts of a plant can produce new plants?

Answer: Plants can use their roots, stems or leaves to produce a new plant.

3. How does the ability of regeneration increase an organism’s chances of survival?

Answer: A missing part makes it difficult for an organism to find food or defend itself. The ability to replace the missing part makes the organism whole and competitive once again.

1. How is budding in yeast cells different from binary fission?

1. When yeast cells reproduce by budding, the division of the cytoplasm is unequal. The larger cell is the parent, and the smaller cell is the bud. In binary fission, the division of the cytoplasm is equal.

2. How can spores survive unfavorable conditions?

2. Spores have a protective outer wall that lets them survive unfavorable conditions. However, as soon as food and water are available, the spore can form a new organism.

3. Why is regeneration considered an example of asexual reproduction?

3. Regeneration is considered an example of asexual reproduction because when an organism loses a part, cells in the organism reproduce to replace the missing part. Some organisms can be cut in half and still grow back the missing part, resulting in the formation of two organisms.

1. Why is resting stage an incorrect term to describe interphase?

Answer: During its life cycle, most of a cell’s time is spent in interphase performing its life functions. The only thing the cell is resting from is mitosis.

2. Identify the event that begins mitosis.

Answer: Replication of the chromosomes signals the end of interphase and the start of mitosis, or cell division. At this point the cell enters a stage of mitosis known as prophase.

3. How can we recognize the prophase stage of mitosis?

Answer: During prophase the nuclear membrane and nucleolus disappear, and the centrioles begin to move to opposite sides of the cell. For the first time we can see astral rays, spindle fibers and chromatids.

4. What are the characteristics of metaphase?

Answer: In metaphase the chromatids are lined up on the spindle fibers in the middle of the cell.

5. How can we recognize the anaphase stage of mitosis?

Answer: In this stage of mitosis, the chromatids separate and move toward opposite sides of the cell.

1. Describe the telophase stage of mitosis.

1. This is the stage of mitosis that results in daughter-cell formation. Each cell has a nucleus with a nucleolus and a pair of centrioles.

2. What is a chromatid?

2. A chromatid is a chromosome and its duplicate held together by a centromere.

3. Why is it important that the cytoplasm divide equally?

3. Equal division of the cytoplasm is important because each daughter cell must end up with

enough cell organelles to carry out the life functions.

4. What is the end result of mitosis?

4. The end result of mitosis is two identical daughter cells, each approximately the same size and containing the same number of chromosomes.

5. How is animal-cell mitosis different from plant-cell mitosis?

5. In animal-cell mitosis, centrioles and astral rays are present. Plant-cell mitosis does not have these structures.

Answer: The advantage of sexual reproduction is variety among the offspring, which inherit some characteristics from each parent. The disadvantage is that two parents are required, so each must find a mate.

1. How is the species number of chromosomes kept the same from one generation to the next in an organism that reproduces sexually?

1. Organisms that reproduce sexually form gametes that have half the species number of chromosomes. When gametes combine during fertilization (n + n), the species number of chromosomes (2n) is restored.

3. How many chromosomes are in a stomach cell of a gorilla if its pancreas cells have 48

chromosomes?

3. The stomach cells of the gorilla have 48 chromosomes. Stomach cells and pancreas cells are somatic cells, and all somatic cells in an organism have the same number of chromosomes.

4. How many chromosomes are in a gamete in an organism that has 30 chromosomes in its somatic cells?

4. A gamete in this organism has 15 chromosomes. Gametes (n) have half the number of chromosomes found in somatic cells (2n). 2n = 30 n = 15

5. What is the diploid number for a cell that has a haploid number of 24?

5. The diploid number for this cell is 48. If the haploid number is n = 24, the diploid number is 2n (2 × 24 = 48).

1. What is the end result of meiosis?

Answer: The end result of meiosis is the formation of gametes with n chromosomes.

2. Describe the process of synapsis and disjunction.

Answer: During synapsis each pair of homologous chromosomes and their replicas come together to form a set of four chromosomes called a tetrad. Disjunction is the breaking up of the tetrad. Two chromosomes go into one cell, and the other two go into another cell.

3. How can we tell if a cell that is just starting to divide will perform meiosis or mitosis?

Answer: If synapsis and tetrad formation take place during prophase, the cell goes through the process of meiosis. However, if a tetrad is not formed and chromatids begin to line up on the spindle fiber, the cell enters mitosis.

1. How does meiosis help maintain the chromosome number of a species?

1. Meiosis is reduction division; somatic cells that have 2n chromosomes produce gametes that have n chromosomes. After fertilization is complete, the number of chromosomes is restored (n + n = 2n). Without meiosis, gametes would have 2n chromosomes; after fertilization there would be 4n (2n + 2n = 4n). After each generation, the chromosome number for the species would double, and soon there would be no room for anything but chromosomes in the cell.

2. How is spermatogenesis in humans different from oogenesis?

2. During spermatogenesis, four sperm cells are produced from each primary spermatocyte. In oogenesis, one ovum is produced along with three polar bodies.

3. Why do the polar bodies produced during oogenesis in humans die?

3. The polar bodies produced during oogenesis die and disintegrate because they have very little cytoplasm and not enough organelles to carry out the life functions of the cell.

4. Discuss the key difference between meiosis and mitosis.

4. The major difference between meiosis and mitosis is that meiosis has two cell divisions, and mitosis has only one. The second cell division in meiosis reduces the number of chromosomes from 2n to n. Meiosis results in the production of four gametes, and mitosis produces two daughter cells.

1. What process produces sperm cells?

Answer: Sperm cells are produced in the testes by the process of gametogenesis. During meiosis one primary spermatocyte produces four sperm cells.

2. Where in the reproductive system of the male are sperm cells stored?

Answer: Sperm cells are stored in the epididymis, where they mature before entering the vas deferens.

3. What contribution do the seminal vesicles make to the reproductive process?

Answer: The seminal vesicles produce one of the three fluids that make up semen. Prior to combining with seminal fluid, sperm cells are not motile. Seminal fluid activates sperm cells and gives them motility.

4. Why is the prostate gland important?

Answer: The prostate gland produces the second of the three fluids that make up semen. The fluid from the prostate gland contains a substance that neutralizes the acid pH of the vagina, which would otherwise kill sperm cells.

5. State the function of bulbourethral glands.

Answer: Bulbourethral glands produce the third fluid found in semen, which contains a substance that neutralizes the acid conditions found in the male’s urethra.

1. Why must the testes be located in the scrotum?

1. The scrotum is a sac located outside the body cavity. The temperature in the scrotum is a few degrees lower than normal body temperature, which is necessary for proper sperm- cell production and development.

5. Outline the pathway that sperm must take to leave the body of a male.

5. Sperm are produced in the testes, stored in the epididymis and then move into the ejaculatory duct. The ejaculatory duct connects to the urethra, which takes the sperm out of the body.

1. What process produces an egg cell?

Answer: Egg cells are produced in the ovaries by the process of oogenesis. During meiosis one primary oocyte produces one egg cell and three polar bodies. This process takes place before a baby girl is born. The purpose of the menstrual cycle is to mature and release an egg for fertilization.

2. Where does fertilization take place?

Answer: In humans fertilization takes place in a fallopian tube.

3. What happens to the egg cell if it is not fertilized?

Answer: If an egg cell is not fertilized, it disintegrates and dies.

1. What is the dual function of the ovaries?

1. The ovaries produce egg cells for reproduction and hormones for regulation. The hormone estrogen regulates female secondary sex characteristics and stimulates the uterus to start producing its capillary lining. Progesterone maintains the uterine lining during the menstrual cycle.

2. Where does development take place?

2. Shortly after fertilization a zygote begins to divide, and the several cells that form implant themselves into the wall of the uterus where an embryo eventually develops. In the uterus, the embryo develops into a fetus.

3. Outline the pathway that sperm must take in the female reproductive system to fertilize an egg.

3. The penis deposits sperm cells into the vagina, and if an egg cell is present, the sperm swim through the cervix, into the uterus and finally into the fallopian tube that contains the egg. Fertilization takes place in the fallopian tube.

4. Why can’t an egg cell be fertilized by more than one sperm cell?

4. After a zygote is produced, a fertilization membrane forms around the zygote, preventing other sperm cells from entering the egg. The head of a sperm cell contains enzymes that can break down the membrane that surrounds the egg. However, these enzymes cannot break down the fertilization membrane because it is made of different proteins, and enzyme action is specific.

1. Which hormone starts the menstrual cycle?

Answer: FSH produced by the anterior pituitary gland starts the menstrual cycle by stimulating follicles to mature an egg and by stimulating the ovary to begin the production of estrogen.

2. Where are follicles found?

Answer: Follicles are cavities located in the ovaries where egg cells are matured during

the menstrual cycle.

3. What is ovulation?

Answer: Ovulation is the release of an egg cell from the ovary.

4. What happens to the follicle after ovulation?

Answer: After ovulation, the follicle is repaired by the growth of a mass of hormone- producing cells called the corpus luteum.

5. How does estrogen get to the uterus?

Answer: Estrogen is a hormone that travels through the blood to reach its target.

1. What are the characteristics of the follicular stage?

1. The follicular stage is the first stage of the menstrual cycle. This stage is dominated by the presence of the follicle. The follicle begins to mature an egg and produce the hormone estrogen.

2. Which hormones regulate the uterine lining?

2. Estrogen begins the development of the uterine lining. Progesterone is responsible for maintaining the uterine lining.

3. What causes the breakdown in the uterine lining?

3. When the level of progesterone is low, the uterine lining begins to break down.

4. How is the uterine lining maintained during pregnancy?

4. Progesterone produced by the developing embryo during pregnancy maintains the

uterine lining.

5. How can we help a woman who is having difficulty ovulating?

5. For a woman to ovulate, an egg must be present and then released. Giving a woman FSH stimulates her follicles to mature an egg; giving her LH results in the release of the egg. FSH and LH are the two hormones found in fertility pills.

1. What is cleavage?

Answer: Cleavage is a special series of mitotic cell divisions, where each time the cells divide they get smaller and smaller. The size of the morula is about the same size as the zygote, yet the morula is a solid ball composed of many cells.

2. Where does embryological development take place?

Answer: Embryological development begins in the fallopian tube with the first cleavage division. By the fifth day the blastocyst is implanted into the wall of the uterus, where embryological development continues until the eighth week, when the embryo is called a fetus.

3. Define differentiation.

Answer: Differentiation occurs at some point between the blastocyst stage and the gastrula stage and results in the cells of the developing embryo becoming different from each other. Certain cells form the eye, others the brain and so on.

How are fraternal twins formed?

1. Sometimes when a woman ovulates, two egg cells are released (each from its own follicle). If each egg cell is fertilized by a different sperm cell, fraternal twins result. Fraternal twins are different from each other genetically.

How are the cells of the gastrula different from those of the blastocyst?

2. The cells of the gastrula are different from each other. Each cell is programmed to become a specific type of tissue or organ in the body. The cells of the blastocyst are undifferentiated and can form any type of tissue or organ in the body.

Why are stem cells important?

3. Stem cells are important because they have the potential of being removed from the blastocyst and used to create tissue and organs that can serve as replacement parts for damaged human organs.

4. Which organ systems develop from each of the three layers in the gastrula?

4. The three layers of the gastrula are the ectoderm, mesoderm and endoderm. The ectoderm layer forms the skin and nervous system. The mesoderm layer forms the skeletal, circulatory and reproductive systems. The endoderm produces the organs of the digestive and respiratory systems.

5. When in human development does sexual reproduction take place?

5. Sexual reproduction takes place at fertilization, when a sperm cell and an egg cell combine to form a zygote. After fertilization, human development takes place asexually by mitosis.

1. What is a fetus?

Answer: A fetus is the name given to an embryo after the eighth week of development.

2. Why is the amnion important?

Answer: The amnion is a sac that contains a fluid called amniotic fluid. The sac and its fluid protect the fetus from shock.

3. What is the function of the umbilical cord?

Answer: The umbilical cord connects the fetus to the placenta and is the fetus’s lifeline. The fetus gets its food, oxygen and water from the placenta through the umbilical cord. Wastes from the fetus pass through the umbilical cord to the placenta.

1. How is the uterine lining maintained during pregnancy?

1. Cells in the placenta produce progesterone, which maintains the uterine lining during pregnancy.

2. What is the placenta?

2. The placenta is a combination of tissue from the mother’s uterine wall and from the developing fetus.

3. How does blood circulate in the fetus?

3. The fetus has its own circulatory system, heart and blood cells for the transport of materials. The baby’s blood and the mother’s blood never mix with each other during development.

4. What is meant by the term gestation?

4. Gestation is the period of time from fertilization to birth and lasts approximately nine months.

1. What is vegetative propagation?

Answer: Vegetative propagation is a form of asexual reproduction by plants. New plants are produced from the root, stem or leaf of an already existing plant.

2. How can one sweet potato produce many new plants?

Answer: A sweet potato placed in water develops many young plants called shoots from the enlarged root. Each of these can produce a new sweet potato plant.

3. How can the eyes of a potato produce new potato plants?

Answer: The eyes of a white potato are actually buds. When one of these buds is removed along with a section of the potato and put into the ground, a new potato plant forms. The starch in the potato serves as food for the developing plant until leaves form and the process of photosynthesis begins, enabling the young plant to produce its own food.

4. What is the difference between a corm and a bulb?

Answer: Bulbs have a short underground stem with thick, fleshy leaves; corms do not have thick, fleshy leaves.

1. Why is vegetative propagation considered asexual reproduction?

1. Vegetative propagation is considered asexual reproduction because new plants are produced from part of an existing plant. Gamete production and seed formation do not take place in vegetative propagation.

2. How is a runner different from a rhizome?

2. A runner is an aboveground stem that grows horizontally along the surface when the stem touches the ground; buds from the stem produce a new plant. A rhizome is an underground stem that grows horizontally along the surface; shoots from buds in the stem develop into new plants.

3. How can one onion bulb produce many new plants?

3. A bulb can produce several smaller bulbs at the base of its short stem. Each of these small bulbs can develop into a new plant.

4. How does the Bryophyllum plant reproduce asexually?

4. When a Bryophyllum leaf falls on moist soil, new “baby” plants can form from the edges of the leaf.

1. What is a cutting?

Answer: A cutting is a root, stem or leaf that is cut off an existing plant and put into water, moist sand or soil to produce a new plant.

2. How are rosebushes produced by layering?

Answer: Roses have long branches that can be bent into the ground and covered with a layer of soil so that a small part of the branch is left sticking out. Roots and stems form from the bent branch. When the bent branch is cut, two separate rose plants are obtained.

3. How can grafting be used to propagate new plants?

Answer: In grafting, a stem (scion) is cut off a plant and attached to the stem of a plant that is rooted in the ground (stock). The fruit produced by this combination is the fruit of the scion.

1. How is natural vegetative propagation different from artificial vegetative propagation?

1. In natural vegetative propagation, a plant reproduces asexually on its own from a part of itself. In artificial vegetative propagation, humans take roots, stems or leaves from existing plants to produce new plants.

2. How are seedless grapes propagated?

2. Seedless grapes are propagated vegetatively by grafting. A scion from a seedless grape vine is grafted onto a stock from a seeded grape vine to produce only seedless grapes.

3. Why would a farmer prefer to plant apple trees produced by grafting rather than trees produced from seed?

3. Farmers always use apple trees or other fruit trees produced by grafting because the fruit of the scion is genetically the same as the plant the scion was taken from. If the tree the scion is taken from produces great-tasting apples, the grafted apple tree produces exactly the same quality of apple. Also, grafted trees mature and produce fruit sooner than those started from seed.

4. What is a disadvantage of vegetative propagation?

4. A disadvantage of vegetative propagation is the lack of variation among the offspring. The offspring can never be better than the parent.

1. What is the function of a flower?

Answer: The flower is the reproductive part of an anthophyte plant.

2. What are the male and female parts of a flower?

Answer: The male part of the flower is the stamen. Remember the men in stamen to help you recall that this is the male part of the flower. The female part of the flower is the pistil.

3. Where are ovules produced?

Answer: The ovules of a flower are produced in the ovary.

4. Where are pollen grains produced?

Answer: Pollen grains are produced in the anther of the stamen.

1. What kind of plant produces flowers?

1. Flowers are produced by plants in the phylum Anthophyta.

2. Why are the petals of a flower important?

2. The petals of a flower are often colored to attract insects, birds and other animals that help in the process of pollination.

3. Why must the stigma be sticky?

3. The stigma is sticky so that when a pollen grain falls on it, the pollen grain doesn’t fall off.

4. Describe the structure and function of a pollen grain.

4. Pollen grains contain the male gametophytes of the flower that fertilize the female gametophytes. Many pollen grains contain three monoploid nuclei, a tube nucleus and two sperm nuclei. Some pollen grains have a tube nucleus and a generative nucleus that divides to produce two sperm nuclei when a pollen tube is formed. A protective outer wall surrounds all pollen grains.

5. Describe the structure and function of the ovule.

5. An ovule is an embryo sac that contains seven cells. One of these is the monoploid (n) egg cell, and another is a cell with two monoploid nuclei that help form the seed. An ovary can contain one or more ovules.

1. What is pollination?

Answer: Pollination is the transfer of pollen from an anther to a stigma.

2. What are the different kinds of pollination?

Answer: The three kinds of pollination are self-pollination, cross-pollination and artificial pollination. Self-pollination is the transfer of pollen from an anther to a stigma within the same flower. Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of another flower. Artificial pollination occurs when humans transfer the pollen.

3. What happens to a flower after fertilization?

Answer: After fertilization takes place, the petals of the flower fall off and the ovary begins to enlarge, eventually becoming a fruit.

1. Describe how fertilization takes place.

1. After a pollen grain lands on a stigma, its protective wall breaks down and a pollen tube forms. The pollen tube grows through the style to the ovary. The two sperm nuclei enter the ovule through an opening called the micropyle to fertilize the egg and the cell that contains the two monoploid nuclei.

2. What is meant by double fertilization?

2. Two fertilizations take place in the ovule. One sperm nucleus fertilizes the egg cell to produce a diploid zygote (2n). The other sperm nucleus combines with a cell that has two monoploid nuclei to form a cell (3n).

3. Why is the 3n cell important?

3. This 3n cell becomes the endosperm of the seed. The endosperm contains starch and provides food for an embryo during germination.

4. What happens to the zygote after fertilization?

4. After fertilization, the zygote becomes the embryo of the seed.

5. What parts of a plant are not fruits?

5. The parts of a plant that are not fruits are the roots, leaves and stems. In some plants these structures can produce new plants by vegetative propagation. Also, all parts of a flower except the ripened ovary are not fruits.

1. Why are seeds important?

Answer: Seeds are important in plant reproduction because they contain the embryo that becomes a new plant. Seeds are important sources of food for humans and animals.

2. What does the epicotyl of a seed become?

Answer: The epicotyl becomes the upper part of the stem and the leaves of the plant.

3. What does the hypocotyl of a seed become?

Answer: The hypocotyl develops into the roots and the lower part of the stem.

How is a monocot seed different from a dicot seed?

1. A dicot seed has two cotyledons, or seed parts, that can be separated from each other. A monocot seed has only one cotyledon.

What is the function of the endosperm?

2. The endosperm of the cotyledon supplies the embryo with food during germination.

Why is the seed coat important?

3. The seed coat protects the seed and its embryo prior to germination.

What is the significance of the micropyle on a seed?

4. The micropyle is a tiny opening in the seed through which the sperm nuclei enter to fertilize the ovule.

1. Why must seeds be dispersed?

Answer: Seed dispersal is necessary to reduce competition between the parent and new plant for scarce resources such as light, soil and water.

2. What are the agents of seed dispersal?

Answer: The agents of seed dispersal are wind, water, insects and other animals. The agents for seed dispersal are the same as those for pollination.

3. Define germination.

Answer: Germination is the breaking of dormancy and the development of a seed into a new plant.

1. Why is fruit important for seed dispersal?

1. Fruit helps disperse the seeds of a plant by attracting animals that eat the fruit and then deposit the seeds at a new location.

2. What is the first part of a seed to germinate?

2. The first part of a seed to germinate is the hypocotyl, which forms the roots needed to anchor the new plant in the soil.

3. What happens to the endosperm after germination?

3. The endosperm provides the embryo with food during germination. After all the endosperm has been used up, the cotyledons that contain the endosperm fall off the stem.

4. Define dormancy.

4. Dormancy is a period of inactivity for a seed, where life functions have been slowed down or temporarily suspended.

1. What are homologous chromosomes?

Answer: Homologous chromosomes are pairs of similar chromosomes found in diploid cells.

2. Define the term dominant.

Answer: In a hybrid or heterozygous individual, where we have two different kinds of alleles for a trait, the characteristic of the trait that we see is called dominant.

3. What is a gene?

Answer: The gene is the hereditary unit or factor that is passed down from one generation to the next. Genes are composed of DNA molecules and determine the characteristics of traits in an organism.

4. What is an allele?

Answer: An allele is different forms of genes for a trait. Alleles occupy corresponding positions on homologous chromosomes. Two alleles determine a trait.

1. How is a trait different from a characteristic?

1. A trait is some distinguishing feature or property of an organism. A characteristic refers to the different versions or expressions of the trait. For example, height is a trait in pea plants; tall or short stems are characteristics.

2. Explain how the homozygous genotype differs from the heterozygous genotype.

2. The homozygous or pure genotype has two of the same kinds of alleles for a trait (for example, TT, two alleles for the tall characteristic of height). The heterozygous or hybrid genotype has two different kinds of alleles for a trait (for example, Tt, an allele for tall and an allele for short).

3. What genotype produces the recessive characteristic of a trait?

3. The only way to get the recessive characteristic of a trait is to have two of the recessive alleles (for example, tt, or homozygous short).

1. State Mendel’s Law of Dominance.

Answer: When an organism has two different alleles for a trait, the characteristic we see is the dominant one.

2. State Mendel’s Law of Segregation.

Answer: When two hybrids are crossed, each allele segregates (separates) during gamete formation so that new allele combinations (genotypes) can be formed at fertilization.

3. How is the Punnett square used to help solve genetic problems?

Answer: The Punnett square is used to show different allelic combinations of gametes and to predict the probability of offspring ratios.

1. What are the results of a hybrid cross by genotype?

1. The result of a hybrid cross by genotype is always 1:2:1, one homozygous dominant to two heterozygous to one homozygous recessive. As a percentage, this ratio is expressed as 25% homozygous dominant to 50% heterozygous to 25% homozygous recessive.

2. Why do the actual results of a genetic cross differ from the predicted results of the Punnett square?

2. The Punnett square can be used as a mathematical tool to predict the possible results that can be obtained from a genetic cross. To get actual results, the genetic cross has to be per- formed. Real-world results are always different from predicted results. However, the larger the sample used, the closer the actual result is to the predicted result. In his experiments, Mendel used large numbers of pea plants.

1. State Mendel’s Law of Independent Assortment.

Answer: In a dihybrid cross, alleles for the different traits separate and are inherited independently of each other.

2. What is a dihybrid?

Answer: A dihybrid has the hybrid (heterozygous) genotype for two different traits. For example, YyRr is a dihybrid. This individual is hybrid for seed color and seed texture.

3. What kind of seeds are produced by a pea plant with the Yyrr genotype?

Answer: Yellow and wrinkled. Yy is hybrid yellow, and rr is homozygous wrinkled.

1. How many kinds of gametes does a dihybrid individual produce?

1. A dihybrid individual can produce four kinds of gametes.

2. How many boxes must a Punnett square have to solve a dihybrid cross?

2. To solve a dihybrid cross, a Punnett square must have 16 boxes. The 4 boxes on each side represent the four possible gametes that can be produced by each dihybrid parent.

3. What is the phenotype ratio that results from the dihybrid cross?

3. The dihybrid cross produces a phenotype ratio of 9:3:3:1. If you memorize this ratio, you will not have to spend the time needed to solve dihybrid cross problems by the Punnett square method.

1. How can we determine the genotype of an organism?

Answer: To determine the genotype of an organism, we do a test cross. We cross the organism having the unknown genotype with a homozygous recessive. If any of the off- spring have the recessive characteristic of the trait, the unknown organism is heterozygous. If all the offspring have the dominant characteristic, the unknown organism is most likely homozygous.

2. When red Japanese four o’clock flowers are crossed with white Japanese four o’clock flowers, plants with pink flowers are produced. What phenotype ratio does crossing two pink-flowered plants produce?

Answer: 25% red, 50% pink and 25% white. This is a 1:2:1 ratio. If you remember the ratio produced when two individuals with the new characteristic are crossed, you do not need to work out the solution with a Punnett square. If you wish to check your answer with a Punnett square, you can use R for the red allele and W for the white allele. The genetic cross that gives the solution is RW × RW.

3. What are the possible results of crossing a Japanese pink four o’clock plant with a white plant?

Answer: 50% pink and 50% white. The genetic cross that gives the answer is RW × WW. Use a Punnett square to find the solution.

1. Why is the homozygous recessive always used in a test cross?

1. The homozygous recessive is always used in a test cross because this organism has a known genotype, two recessive alleles for a trait. An organism with the dominant characteristic cannot be used because we don’t know if it is homozygous or heterozygous. We would not know the genotype of the test organism or the genotype of the organism it is being crossed with. The results obtained from crossing two unknown genotypes cannot lead to any conclusions as to their allele combinations.

2. How is incomplete dominance different from codominance?

2. In incomplete dominance, we have two different alleles for a trait and neither is dominant. In codominance, both alleles are dominant.

3. In cattle, an animal with a red coat crossed with one that has a white coat produces offspring that are roan (animals with both red and white hair). What phenotype ratio is produced in the offspring when two roan animals are cross

3. The genotype ratio produced is 25% red, 50% roan and 25% white. To solve this problem, use CR for the red allele and CW for the white allele. The genetic cross that gives the answer is CR CW × CR CW. Use a Punnett square to find the solution.

3. All gametes have one sex chromosome. A sperm cell can have an X or Y sex chromosome.Egg cells contain only X sex chromosomes.

4. Which parent determines the sex of the child?

4. The male parent determines the sex of the child.

5. When is the sex of a new individual determined?

5. The sex of a new individual is determined at the instant of fertilization when the sperm and egg cells combine.

1. What are the four different blood types?

Answer: The four different blood types are A, B, AB, and O. The type of antigen present on the surface of the red blood cell determines the blood type of the individual.

2. What types of antigens are on the red blood cells of people with type A, B, AB, and O blood?

Answer: People with type A blood have antigen A on the red blood cell. Individuals with type B blood have antigen B. Those with type AB blood have antigens A and B. Finally, people with type O blood do not have any antigens on their red blood cells.

3. What types of antibodies are in the plasma of people with type A, B, AB and O blood?

Answer: People with type A blood have antibody B in their plasma. Individuals with type B blood have antibody A. Those with type AB blood do not have antibodies A or B in their plasma. People with type O blood have antibodies A and B.

4. What is a blood transfusion? Answer: A blood transfusion is the transfer of blood from one individual to another. The donor’s blood is matched to the recipient’s blood whenever possible. 5. How many alleles control the different blood types?

Answer: Three alleles control human blood types. Six different genotypes are possible for the four blood types. Look at the preceding table for the different genotype combinations.

1. Why can a person with type O blood donate to anyone in an emergency?

1. A person with type O blood can donate to anyone in an emergency because type O blood does not contain antigens on the red bloods cell that can cause agglutination or clumping of the blood.

2. Why can’t a person with type A blood donate to a person with type B blood?

2. A person with blood type A cannot donate blood to a person with blood type B. The type A individual has anti-B antibodies that cause agglutination with antigen B in a person with blood type B.

1. What are sex-linked traits?

Answer: Sex-linked traits are traits that have an allele located on the X chromosome and sometimes on the Y chromosome. Two examples of sex-linked traits are hemophilia and color blindness.

2. Who can be a carrier of a sex-linked disease?

Answer: A carrier is a female that has an allele for a sex-linked disease but does not have the disease.

3. How can we tell whether a person has hemophilia?

Answer: A person with hemophilia who gets a cut or bruise does not stop bleeding because the individual is missing a clotting factor in the blood.

4. What is the genotype of a woman who is color blind?

Answer: The genotype of a color blind woman is XnXn, or homozygous recessive.

5. From which parent does a son inherit a sex-linked allele?

Answer: A son inherits a sex-linked allele from his mother. If a woman is heterozygous, her son has a 50% chance of having a sex-linked disease. A daughter can inherit a sex-linked allele from her mother or father.

1. What is the function of a pedigree chart?

Answer: In genetics a pedigree chart is used to keep track of a trait in a family from one generation to the next.

2. How are different generations indicated on a pedigree chart?

Answer: On a pedigree chart, different generations are indicated by the use of Roman numerals. The parent generation is generation I, and their offspring are in generation II.

3. How is a married couple indicated on a pedigree chart?

Answer: To indicate that a couple is married or has mated, a horizontal line is drawn between a circle (female) and a square (male).

1. What factors determine the phenotype of an organism?

Answer: The phenotype of an organism is determined by its genotype and any environmental factors that can influence the expression of certain alleles.

2. Why do the Himalayan rabbit and the Siamese cat have darker fur on their ears, nose, feet, and tail?

Answer: Some organisms have darker extremities because they have an allele that produces a heat-sensitive enzyme, which promotes melanin production. In warm areas, the enzyme is less active; less melanin is produced, and the fur of the animal is lighter. In the cooler extremities, the enzyme is more active; more melanin is produced, and the fur in these areas is darker.

1. Why are identical twins used in studies that investigate the influence of environment on heredity?

1. Identical twins are used in studies that investigate the influence of environment on heredity because they have the same heredity (genes). Thus, the only variable in the study is the specific environmental influence that is being investigated.

2. When Serratia marcescens bacteria are grown at a temperature of 30°C, the colonies that form are cream colored. The same bacteria grown at 25°C produce colonies that are red. How can we explain this difference in color?

2. The difference in the color of the bacteria can be explained by the effect of temperature on the expression of the allele that controls color.

3. Why is it advantageous for the arctic fox to be white in color during the winter?

3. The white fur color in winter allows the fox to blend in with the snow in its environment. This helps the fox be a more efficient predator and, at the same time, enables the fox to avoid animals that might consider it prey.

1. What is the shape of the DNA molecule?

Answer: The DNA molecule is a double helix. Watson and Crick discovered this in 1953.

2. What is the structure of a DNA molecule?

Answer: The DNA molecule is composed of thousands to millions of repeating nucleotides.

3. What are the parts of a DNA nucleotide?

Answer: A nucleotide contains deoxyribose, a phosphate group and one of four possible nitrogen bases.

4. What are the names of the four possible nitrogen bases in a nucleotide?

Answer: The four possible nitrogen bases in a nucleotide are adenine (A), guanine (G), cytosine (C), and thymine (T).

5. When does the DNA molecule replicate?

Answer: The DNA molecule replicates when the chromosome that it is in replicates. During mitosis, replication takes place at the very end of interphase.

1. How are the paired nucleotides of the DNA molecule held together?

1. The paired nucleotides of the DNA molecule are held together by weak hydrogen bonds. The weak hydrogen bonds allow the molecule to easily separate or unzip during replication and to recombine when replication is complete.

2. How are the deoxyribose molecules in DNA held together?

2. The deoxyribose molecules in DNA are held together by phosphate groups.

3. What is the nitrogen-base sequence of a DNA strand if the sequence of bases in the complementary strand is A-C-T-G-T-C?

3. The complementary strand to A-C-T-G-T-C is T-G-A-C-A-G. In a DNA molecule, adenine pairs with thymine, and cytosine pairs with guanine.

4. How does a DNA molecule replicate?

4. A DNA molecule replicates when its two strands unzip, and nucleotides in the cell pair up with their complements on each original strand. At the completion of replication, two molecules of DNA are formed. Each molecule is composed of one old (original) strand and one new strand.

5. What is semiconservative replication?

5. In semiconservative replication, each molecule that is formed has one old (original) strand and one new strand.

1. Where does protein synthesis take place?

Answer: Protein synthesis takes place at the ribosome. Ribosomes can be found attached to the endoplasmic reticulum or floating free in the cytoplasm.

2. Why are proteins important for a cell?

Answer: Proteins are used for growth, repair and reproduction of new cells. DNA and RNA are important nucleoproteins. The kinds of proteins that we have determine our traits.

3. Where is messenger RNA (mRNA) made? Answer: mRNA is made in the nucleus and then travels into the cytoplasm where it attaches to a ribosome. 4. What is a codon?

Answer: A codon is genetic code, a set of three nitrogen bases in DNA or mRNA.

1. How does DNA differ from RNA?

1. DNA is a double helix, contains deoxyribose, and one of its nitrogen bases is thymine. RNA is a single helix, contains ribose, and has uracil instead of the nitrogen base thymine. DNA is found in the nucleus, and RNA is found in the cytoplasm.

2. Describe the process of transcription.

2. Transcription is a process that produces RNA nucleoproteins. Transcription begins when a segment of DNA unzips, and one strand acts as a template for the formation of single- stranded mRNA. Complementary nitrogen bases pair up with bases on DNA to form mRNA. When the mRNA molecule is complete, it separates from the DNA and leaves the nucleus. At this point, each DNA strand recombines with its complement.

3. Describe the process of translation.

3. Translation is the process by which the ribosome combines amino acids to produce proteins. The function of transfer RNA (tRNA) molecules is to bring amino acids to mRNA at the ribosome. The ribosome moves down the mRNA molecule, and the amino acids are attached to each other by peptide bonds that form by dehydration synthesis. When the protein has been formed, the tRNA molecules separate from the ribosome (as does the newly formed protein).

4. How does mRNA differ from tRNA?

4. mRNAand tRNA differ in both structure and function. mRNA is a long, single-stranded nucleoprotein with many codons that have the information needed to direct the order of amino acids in a protein. tRNA molecules have two sides. One side of a tRNA molecule attaches to an amino acid; the other side has an anticodon that is complementary to a codon on mRNA. tRNA molecules bring amino acids to the correct location on an mRNA molecule.

5. A segment of a DNA molecule has the nitrogen base sequence T-A-C. What would be the nitrogen base sequence of the tRNA anticodon?

5. The sequence of nitrogen bases on the tRNA anticodon is U-A-C. This answer is obtained by first finding the complementary nitrogen base sequence of the mRNA molecule, which is A-U-G. The complement of T is A, the complement of A is U (RNA has the nitrogen base uracil instead of thymine), and the complement of C is G. The tRNA anticodon is the complement of mRNA. mRNA is A-U-G. The complement of A is U, the complement of U is A, and the complement of G is C. This gives us the answer U-A-C.

1. What are mutations?

Answer: A mutation is a change or error in a gene or chromosome.

2. What are the different types of mutations?

Answer: The different types of mutations are gene mutations and chromosomal mutations. Gene mutations can be point or frameshift mutations. Chromosomal mutations that result from nondisjunction change the chromosome number of the organism. Structural mutations can occur because of deletions, additions, translocations, or inversions.

3. List some of the causes of mutations.

Answer: Mutations can be caused by environmental factors such as ultraviolet rays and cosmic rays. Another cause of mutations results from mutagenic agents such as X-rays, gamma rays, nuclear radiation, and carcinogens.

4. How can a mutation be passed down from one generation to the next?

Answer: Mutations can be passed down from one generation to the next if a gamete containing a mutated allele or chromosome takes part in the fertilization process.

5. What is a carcinogen? Give some examples.

Answer: Carcinogens are chemicals that cause gene mutations, which can result in cancer. Some examples of carcinogens are asbestos, benzene, some food dyes, and PCBs.

1. Explain how a point mutation takes place.

1. When a point mutation occurs, one nitrogen base in a codon is replaced by another nitrogen base. The number of bases in the codon remains the same (three), and only one codon is affected. The changed codon results in a different amino acid in the polypeptide that is being synthesized.

2. Explain how a frameshift mutation takes place.

2. In a frameshift mutation, one nitrogen base is added or deleted from a codon on an mRNA molecule. In a deletion, a nitrogen base is removed; all the remaining nitrogen bases shift to the left, and every codon after the deletion has a new set of three nitrogen bases. In an addition, a nitrogen base is inserted. This forces the nitrogen bases to shift to the right, and each codon then has a new set of three nitrogen bases.

3. How does nondisjunction result in chromosomal mutations?

3. When nondisjunction occurs during meiosis, chromosomes fail to separate, and a change in chromosome number results. One gamete has an extra chromosome, and the other gamete is missing one chromosome. After fertilization a zygote is produced that has 2n + 1 or 2n – 1 chromosomes.

4. How is the type of chromosomal mutation known as an addition different from a translocation?

4. In an addition, a segment of chromosome breaks off and is added to its homologous chromosome. However, in translocation, a segment of chromosome breaks off and is added to a different (nonhomologous) chromosome.

Answer: Mutations result in the production of defective alleles that can be inherited. These defective alleles are responsible for many genetic diseases in humans.

2. What is the probability of a child having cystic fibrosis if both parents are heterozygous for the allele that causes the disease?

Answer: The chance of this child having cystic fibrosis is 25%. This is a hybrid cross, and the ratio produced by a hybrid cross is always 3:1. The chance of having a child with cystic fibrosis is one in four (25%). A person must have two recessive alleles to have this genetic disease. If N represents the normal allele, and n represents the defective recessive allele, the cross that gives the result is Nn × Nn. Use a Punnett square to solve this problem.

3. How can a child born with PKU disease avoid the symptoms of this disease?

Answer: A child that tests positive for PKU disease is put on a special diet that is low in phenylalanine to control this disease. High levels of phenylalanine lead to nervous system problems, mental retardation and decreased body growth. Preventing high levels of phenylalanine avoids these complications.

4. Why doesn’t an individual that is heterozygous for Tay-Sachs disease have the disease?

Answer: Tay-Sachs disease results when an individual has two recessive alleles that are defective for the production of the enzyme called Hex-A. A heterozygous individual has one normal allele for the production of this enzyme. As long as one allele is working to produce Hex-A, the individual does not have the disease.

5. How are sickle-cell red blood cells different from normal red blood cells?

Answer: Normal red blood cells are round, and sickle-cell red blood cells are crescent shaped. The sickle cells tend to block the flow of blood in small blood vessels.

1. How is Huntington’s disease different from most other genetic diseases?

1. Huntington’s disease is caused by one defective dominant allele. Most other human genetic diseases are caused by the presence of two recessive alleles. In Huntington’s disease, the presence of a protein damages nerve cells in the brain. In some recessive genetic diseases, the absence of a protein (usually an enzyme) causes the disease. Examples of this can be seen with Tay-Sachs disease and PKU.

2. A man has Huntington’s disease, and his wife does not have an allele for the disease. What are their chances of having a child that will develop Huntington’s disease?

2. Their chances of having a child that will develop Huntington’s disease is 50%. To have Huntington’s disease a person needs to have only one defective dominant allele for the disease. If H represents the allele for Huntington’s disease, and h represents the normal allele, the genotype for the man is Hh and for the woman is hh. The cross that gives the result is Hh × hh. Use a Punnett square to find the solution.

3. What is the probability that a child will have sickle-cell anemia if both parents have the sickle-cell trait?

3. The probability that this child will have sickle-cell anemia is 25%. This is the hybrid cross again. The ratio produced by a hybrid cross is always 3:1. The chance is one in four (25%) of this child having sickle-cell anemia. A person must have two recessive alleles to have this genetic disease. The key used to represent the alleles in this problem is different from others that we have seen. HbA represents the normal allele, and HbS represents the defective recessive allele. The letters Hb represent the hemoglobin molecule. Actually, any letter combination can be used that makes sense to you when solving genetic problems. The cross that gives the result is HbAHbS × HbAHbS. Use a Punnett square to solve this problem.

4. Can a couple have a child with Tay-Sachs disease if one parent is heterozygous for the disease and the other parent is homozygous normal?

4. No. This child of these parents has a 0% chance of having Tay-Sachs disease. The child must have two defective recessive alleles to have the disease. This cannot occur given the genotypes of the parents. If N represents the normal allele, and n represents the defective recessive allele, the cross that gives the result is Nn × NN. Use a Punnett square to find the solution.

5. How can a couple determine whether they are at risk of having a child with a genetic disease?

5. A simple blood test can be done to determine whether either of the prospective parents carries an allele for a genetic disease. Genetic counseling of the parents can help them determine the risk factors they face when having children.

1. What is biotechnology?

Answer: Biotechnology involves the use of engineering and technology to advance biological research. Some applications of biotechnology are in the areas of gene sequencing, genetic engineering, cloning, and stem cell research.

2. What were the goals of the Human Genome Project?

Answer: The three key goals of the Human Genome Project were to determine the sequences of the 3 billion nitrogen base pairs in DNA, identify the 30,000 genes in human DNA, and create a database to store this information that would be available to researchers.

3. Why is the Human Genome Project important?

Answer: The Human Genome Project is important because it will enhance our knowledge of gene function and lead to the discovery of new methods of diagnosing and treating disease.

4. What is genetic engineering?

Answer: Genetic engineering is a technique used to transfer genes from the chromosomes of one species into the chromosomes of another species.

5. What is a vector?

Answer: A vector is a carrier used to bring DNA into other cells. Viruses and bacterial plasmids are examples of commonly used vectors.

1. How can genes be removed from the chromosome of one species and inserted into the chromosome of another species?

1. The restriction enzyme endonuclease can be used to cut a gene out of the DNA from one chromosome, and the enzyme DNA ligase can be used to splice the inserted gene into another chromosome. This technique results in the production of a recombinant DNA molecule.

2. What are plasmids?

2. Plasmids are pieces of circular DNA in bacteria that are often used in gene splicing. A spliced plasmid can be inserted into other cells.

3. How can an organism be cloned?

3. One method of cloning involves removal of the nucleus from a somatic cell and its insertion into an unfertilized egg cell that has had its nucleus removed. An embryo develops that becomes a new individual, identical to the one that donated the nucleus.

4. Why is stem cell research controversial?

4. Stem cells are obtained from the blastocyst stage of embryological development. To harvest stem cells, the embryo is destroyed. Many people feel human life begins at conception and the destruction of an embryo prevents the formation of a new individual. Others feel that an embryo is not a human and that the benefits to be derived from stem cell research are of primary importance.

5. What are three ways to produce an embryo?

5. The traditional method of embryo production involves the union of egg and sperm cells at fertilization to produce a zygote. This zygote becomes an embryo as a result of cleavage. Cloning and parthenogenesis are two biotechnological methods of embryo production.

1. Define evolution.

Answer: Evolution is the change that has occurred in a species of organism with the passage of time.

2. What is a fossil?

Answer: A fossil is the remains of an organism that lived in the past.

3. Why are the soft parts of organisms rarely fossilized?

Answer: The soft parts of organisms are rarely fossilized because they decay rapidly after the death of the organism. The hard parts of the organism decay slowly and can form fossils.

4. What is amber?

Answer: Amber is a form of fossilized resin from trees that can contain trapped insects or plant material.

5. How does refrigeration result in fossil formation?

Answer: Refrigeration results in fossil formation because cold temperatures can dramatically slow down the process of decay.

1. Why is the study of evolution important?

1. Evolution shows how organisms have changed over time. Evolution accounts for the huge diversity of living things that exist on earth.

2. Why is the fossil record strong evidence for evolution?

2. Fossils are strong evidence in support of evolution because they are the tangible remains of organisms that have lived in the past. Fossils can be compared to current organisms so that any changes that have taken place can be determined.

3. How are imprints different from molds?

3. An imprint is an impression of a part of an organism. Examples of imprints are leaf prints and footprints. A mold is an outline of the organism that is left behind after the organism dies, becomes covered with sand or mud, and then decays.

4. How do tar pits help form fossils?

4. Tar pits contain asphalt that surrounds the bones of the organism preventing the bacteria of decay from breaking down the bones. These preserved bones eventually become fossils.

5. Describe the process of petrifaction.

5. Petrifaction occurs when minerals in water diffuse into the cells of a dead organism, forming rock.

1. What kind of rock are fossils found in?

Answer: Fossils are found in sedimentary rock.

2. Why are fossils dated?

Answer: Fossils are dated to determine when the organism that formed the fossil was alive.

3. Why aren’t fossils found in igneous rock?

Answer: Igneous rock is formed by volcanic activity and lava flow. The high temperatures associated with this type of rock formation destroy any organisms, preventing the for- mation of fossils.

4. Why can’t carbon-14 dating be used for fossils that are more than 50,000–70,000 years old?

Answer: The half-life of carbon-14 is short (5,730 years), so after 50,000–70,000 years not enough carbon-14 is left in a fossil to be measured.

1. How does the relative dating of fossils work?

1. In relative dating, the age of a fossil is not determined. However, the age of one fossil relative to another can be determined. For example, fossils in layers near the top of a rock formation are younger than fossils near the bottom.

2. What is an index fossil?

2. An index fossil represents a species of organism that was found all over the world but lived for a short period of time. If the age of an index fossil is known, it can be used to determine the age of other fossils in the same layer. In addition, fossils in layers above the index fossil are younger. Fossils in layers below the index fossil are older.

3. What is absolute dating?

3. Absolute dating gives an approximate date of when the organism represented by a fossil died. Absolute dating relies on the radioactivity of certain elements and their half-life. The older the fossil, the more the radioactive element has decayed.

4. How does carbon-14 dating work?

4. Carbon-14 dating is a form of absolute dating. Carbon-14 has a half-life of 5,730 years. The carbon-14 in a fossil sample decays into half its original amount every 5,730 years. A sample that has one-eighth the original amount of carbon-14 has gone through three half- lives and is 3 × 5,730 (or 17,190) years old.

5. Why can’t carbon-14 be used to date a rock?

5. Rocks generally don’t contain carbon, so trying to use carbon-14 to date a rock is meaningless. Carbon-14 dating can be used to date fossils that contain carbon, such as bones and teeth (hard parts). To date rocks that might contain fossils, uranium 238 and the potassium-argon method can be used.

1. What are homologous structures?

Answer: Homologous structures are similar in construction and evolutionary development but dissimilar in function. Homologous structures are often used to show evolutionary relationships between organisms. Examples of homologous structures are the forelimb of a human and the wing of a bat.

2. What are analogous structures?

Answer: Analogous structures are similar in function but dissimilar in construction and evolutionary development. Examples of analogous structures are the wing of a bird and the wing of an insect.

3. How do vestigial structures provide evidence of evolution?

Answer: A vestigial structure at one time had a function but no longer has a function. The change from functionality to nonfunctionality demonstrates evolution. For example, at one time the human appendix had a digestive function but now does not. This change shows that humans have evolved.

1. Explain the concept of common ancestry.

1. A common ancestor is an individual from which two or more related species could have evolved.

2. How does comparative anatomy provide evidence for evolution?

2. Comparative anatomy is a technique used to compare homologous body structures of organisms. The more the structures are similar to each other, the closer the evolutionary relationship is between the organisms.

3. Scientists have found skeletons of camels dating back millions of years. Early skeletons of camels show that this animal was once smaller and different from modern-day camels. How can this information be used to provide evidence of evolution?

3. If fossilized camel skeletons from different points in history are compared, the differences between them shows a pattern of change that proves evolution occurred.

4. How does comparative embryology provide evidence for evolution?

4. The similarity between embryos during the early stages of development supports the concept of the common ancestor.

5. How does comparative biochemistry provide evidence for evolution?

5. Comparative biochemistry provides strong evidence for evolution. The close similarity in complex molecules found between different species argues in favor of a common ancestor from which organisms could have evolved (changed). For example, human insulin differs from cow insulin in only 3 out of 51 amino acids. Cow insulin is close enough to human insulin that it can be given to diabetics.

1. According to Darwin, what is the result of overproduction?

Answer: The result of overproduction is competition for scarce resources such as food, water, and territory.

2. What is meant by variation?

Answer: Variation refers to the different and diverse forms of a trait.

3. How are the most-fit or best variations in a population selected?

Answer: According to Darwin, the best variations are selected by nature. The modern approach to evolution states that nature selects the organisms with alleles for the fittest variations; these organisms are the ones most likely to reproduce and pass on the alleles for these variations to the next generation.

4. Which theory of evolution is best described by gradualism?

Answer: Darwin’s theory of natural selection is best described by gradualism, which states that evolution is a gradual, slow and continuous process that proceeds in numerous small steps over many generations.

1. Explain the concept of acquired characteristics.

1. According to the concept of acquired characteristics, the more an organism uses a structure, the better and more highly developed the structure becomes. The acquired improvement can be inherited by the offspring.

2. What did Darwin mean by survival of the fittest?

2. To Darwin, survival of the fittest meant that those individuals that had the most-fit variations got the opportunity to reproduce and to pass these variations on to the next generation.

3. How did Darwin account for the formation of new species?

3. Darwin believed that with the passage of time, the most-fit variations became the norm within a population, eventually giving rise to a new species of organism.

4. How does the concept of mutations update Darwin’s theory of natural selection?

4. The concept of mutations is used to explain how variations can occur in a species of organism.

5. What is the punctuated equilibrium explanation for the rate of evolution?

5. The punctuated equilibrium explanation of evolution states that change occurs in sudden spurts during which many species are formed, followed by long periods of stability with no speciation.

1. State the Hardy-Weinberg law.

Answer: Within a population, the frequency of an allele remains constant from generation to generation, as long as certain conditions are met.

2. State the two mathematical equations used to express the Hardy-Weinberg law.

Answer: The two mathematical equations used to express the Hardy-Weinberg law are p+q=1 and p2 +2pq+q2 =1.

3. Why must the gene pool be large for the Hardy-Weinberg law to work?

Answer: An increase in the size of the gene pool creates an increase in statistical accuracy.

4. How does migration into or out of a population affect the Hardy-Weinberg law?

Answer: Migrations of individuals into or out of a population changes the frequency of alleles in a population.

5. In a population of fruit flies, the percentage of individuals with the dominant allele for red eyes is 80%. What is the percentage of the recessive allele for white eyes?

Answer: Twenty percent of the fruit flies have the recessive allele for white eyes. The equation p + q = 1 can be used to solve the problem. Here, p is the percentage of individuals with the dominant allele (0.8 or 80%), and q is the percentage of individuals with the recessive allele. p+q=1 0.8 + q = 1 q = 0.2 or 20%

1. What is geographic isolation?

1. Geographic isolation is the physical separation of individuals within a population and is caused by geographical barriers such as mountains, deserts, oceans, and rivers.

2. How does geographic isolation upset the Hardy-Weinberg law?

2. Geographic isolation upsets the Hardy-Weinberg law by reducing the size of the gene pool and interfering with random mating.

3. How can environmental factors upset the Hardy-Weinberg law?

3. Environmental factors upset the Hardy-Weinberg law by selecting one variation within a population over another.

4. How can the Hardy-Weinberg law be used to indicate that evolution is taking place?

4. The Hardy-Weinberg law states that within a population the frequency of an allele remains constant. Any change in the frequency of an allele in a population might indicate that evolution is taking place.

1. Identify the gases that were present in the earth’s primitive atmosphere.

Answer: The gases that were probably present in this atmosphere were: water vapor, nitrogen, carbon monoxide, carbon dioxide, and some hydrogen.

2. Name the organic molecules that were the first to form on earth.

Answer: Some of the first organic molecules to form on earth were simple sugars, amino acids, fatty acids, glycerol, and nucleotides.

3. What kind of cells were the first cells on earth?

Answer: According to the heterotroph hypothesis, the first cells to originate on earth were primitive prokaryotic heterotrophs.

1. How was carbon dioxide added to the earth’s atmosphere?

1. Carbon dioxide was added to the earth’s atmosphere by anaerobic respiration of the first heterotrophs.

2. How are modern-day heterotrophs different from the first heterotrophs on earth?

2. The first heterotrophs were prokaryotic, reproduced by binary fission, and produced energy by fermentation (anaerobic respiration). Modern-day heterotrophs are eukaryotic, reproduce by mitosis, have mitochondria, and produce energy by aerobic respiration.

3. State the main concept of the endosymbiotic theory.

3. The endosymbiotic theory states that eukaryotic cells incorporated primitive prokaryotic cells that eventually evolved to become mitochondria and chloroplasts.

1. Define ecology.

Answer: Ecology is the branch of biology that studies living things, their interrelationships with each other and their interrelationship with the environment. Two interrelationships exist. The first is between living things. The second is between living things and their environment.

2. How are abiotic factors different from biotic factors?

Answer: Abiotic factors are all the nonliving things in the environment such as climate, light, temperature, water, and soil. Biotic factors are all the living things that are found in the environment.

3. How is humus formed?

Answer: Humus is the part of soil that is formed from decayed plant and animal material. Humus provides nutrients and minerals for plants and increases the capability of soil to retain water.

How do latitude and geography affect climate?

1. Generally the further a location is north or south of the equator, the colder the climate. Geographical features such as mountains, proximity to water, and elevation affect climate. One side of a mountain range can have lots of rainfall, while the other side is a desert. Locations close to water tend to be cooler in summer and warmer in winter. Higher elevations tend to have colder climates.

How are light, temperature and water interrelated?

2. The greater the duration and intensity of light in a given location, the higher the temperature. High temperatures in an area increase evaporation from bodies of water and increase transpiration, which is the loss of water from the leaves of a plant.

Why can’t cactus plants survive outdoors in the northern United States and Canada?

3. The abiotic conditions of the northern United States and Canada are very different from those found in desert regions where cactus plants grow. The cold winters, excess precipitation, different soil conditions, reduced duration of light, and reduced intensity of light are factors that prevent cactus plants from surviving in the northern United States and Canada.

1. How does a population differ from a community?

Answer: A population contains members of the same species that live together in a specific location, while a community has several different populations that live together in a specific location.

2. What is an ecosystem?

Answer: An ecosystem consists of a community and the abiotic factors in its environment.

3. How is habitat different from niche?

Answer: Habitat is where an organism lives in its environment. Niche is the role or job that the organism has.

1. How does the carrying capacity of the land affect a prey population?

1. The carrying capacity of the land refers to the land’s capability to supply enough food to feed a population. When the number of individuals in a population exceeds the carrying capacity of the land, some members of the population must migrate to a new location or some will die of starvation.

2. How does intraspecific competition differ from interspecific competition?

2. Intraspecific competition is competition between members of the same species. Interspecific competition is competition between members of different species. Organisms compete for territory, food and water. In the case of intraspecific competition, organisms also compete for a mate.

3. Explain the predator-prey relationship.

3. A predator is an animal that hunts and kills for food; the prey is the animal that is hunted. When the prey population increases, the predator population also increases. As the prey population decreases, the predator population decreases. Predators are important because they keep the prey population from increasing to the point where it exceeds the carrying capacity of the land.

1. Define symbiosis.

Answer: Symbiosis is a relationship between two organisms that live together where at least one of the organisms benefits from the association.

2. Define commensalism.

Answer: Commensalism is a relationship where one organism benefits from the association, and the other is neither helped nor harmed.

3. What is coevolution?

Answer: Coevolution is a process by which species adapt to changes in one another.

1. Which type of symbiosis is beneficial to both organisms in a relationship?

1. Mutualism is a symbiotic relationship that is beneficial to both organisms.

2. Bees and other insects visit flowers for pollen, which they use as food. In the process of visiting a flower, insects help transfer pollen from the anther to the stigma. Identify the type of symbiosis described here.

2. Mutualism is the type of symbiosis described here. The insects benefit by gathering pollen for food. The plants benefit by having their flowers pollinated so that they can reproduce.

3. Why is parasitism detrimental to the host?

3. The parasite uses the host for a place to live and a source of food. The host is an unwilling participant in this relationship and is injured or killed by the parasite.

1. What is the source of energy that flows through an ecosystem?

Answer: The sun is the source of energy that flows through the ecosystem.

2. What does a food chain show?

Answer: A food chain shows how energy is transferred from one organism to another in an ecosystem.

3. How is a predator different from a scavenger?

Answer: A predator is a heterotroph that hunts and kills its prey to obtain food for energy. Predators are carnivores and are primary, secondary or tertiary consumers. A scavenger is a carnivore that eats food left over by predators. Scavengers do not kill the animals they eat.

1. Why is the flow of energy through an ecosystem considered unidirectional?

1. The flow of energy through an ecosystem is considered unidirectional because energy is never recycled. Energy never returns to the sun.

2. Why do food chains rarely exceed four consumers?

2. As energy flows through the food chain from one group of organisms to the next, less energy is available because each group uses up energy for life functions such as locomotion, respiration, digestion, and reproduction.

3. Why is it better for an organism to be part of a food web as opposed to a food chain?

3. Organisms in food webs have the opportunity to eat other foods if one food becomes unavailable. However, an organism in a food chain has only one choice of food. If that food is not available, the organism in the food chain dies.

1. Define recycling.

Answer: In ecology, recycling refers to the reuse of important abiotic factors such as water, oxygen, carbon dioxide, and nitrogen.

2. Identify the abiotic factor from the environment that is never recycled.

Answer: Light energy from the sun is never recycled. The flow of energy through an ecosystem is unidirectional.

3. How does water enter the atmosphere?

Answer: Water can enter the atmosphere by evaporation from oceans, lakes, and rivers. Water also enters the atmosphere by transpiration from plants.

1. How does the sun play an important role in the water cycle?

1. The sun provides the energy needed for the evaporation of water from oceans, lakes, and rivers. This water condenses to form clouds, and precipitation returns the water to the oceans, lakes, and rivers for collection so that the process can begin again.

2. Identify the two biological processes that are involved with the oxygen/carbon dioxide cycle.

2. The two biological processes involved in the oxygen/carbon dioxide cycle are photosyn- thesis and respiration. Photosynthesis is a process that puts oxygen into the atmosphere and removes carbon dioxide. Respiration uses oxygen and puts carbon dioxide into the atmosphere. See Chapter 6 for a comparison of respiration and photosynthesis.

3. Explain why the amount of carbon dioxide that is introduced into the atmosphere exceeds the amount of oxygen used during aerobic respiration.

3. The amount of carbon dioxide that is introduced into the atmosphere exceeds the amount of oxygen used during aerobic respiration because additional carbon dioxide is added by decomposers, the burning of fossil fuels and the burning of forests.

4. What are the different kinds of bacteria in the nitrogen cycle? Give the function of each.

4. Four different kinds of bacteria are involved in the nitrogen cycle:❑ Nitrogen-fixing bacteria take free nitrogen from the atmosphere and produce nitrates. ❑ Bacteria of decay are responsible for breaking down dead plants and animals into ammonia. ❑ Denitrifying bacteria convert ammonia into free nitrogen. ❑ Nitrifying bacteria convert ammonia into nitrites.

1. What is succession?

Answer: Succession is a process by which one biotic community is replaced by another until a climax community of plants and animals develops.

2. What are some of the causes of succession?

Answer: The current community in an area often changes the physical conditions of its environment so that it is no longer favorable for it to continue living there. When this happens, it is replaced (succeeded) by a community that can survive under the altered conditions. A change in the climate of an area often makes conditions unfavorable for one community and more favorable for another.

3. What is a pioneer organism?

Answer: A pioneer organism is the first organism to occupy an area. Lichens are an example of pioneer organisms.

1. How does primary succession differ from secondary succession?

1. Primary succession begins in an area that never had life. Secondary succession occurs in areas where life has previously existed. Secondary succession often follows a catastrophe that destroys an existing community.

2. What is a climax community?

2. A climax community is the last community to occupy an area. A climax community is stable and self-perpetuating.

3. How can a climax community be destroyed?

3. A climax community can be destroyed by fires, volcanic eruptions, hurricanes, changes in climate, or human activities.

1. Define a biome.

Answer: A biome is a large geographical area having one kind of climate and a climax community of unique plants and animals.

2. Why can’t trees grow in the tundra?

Answer: Trees cannot grow in the tundra because of permafrost, a condition where the ground is permanently frozen. The root system of trees cannot grow in frozen soil.

3. Which biome is the most stable and least changing?

Answer: The most stable and least changing biome is the marine biome. Climate has very little effect on this biome. The temperature of the water at any given depth in the ocean varies within narrow limits. The salinity of water remains relatively constant at 3.5%.

1. How do abiotic factors such as climate determine the kinds and distribution of plants in a biome?

1. The abiotic factors of the environment limit the kinds of plants and animals that are in a biome. As a result, each biome has its own unique plant and animal life. The trees of the taiga and the temperate deciduous forest cannot survive in the tundra because of permafrost. Tropical rain forest plants cannot survive in the desert because of insufficient rainfall. Rain forest plants can’t grow in a marine biome.

2. How are desert plants adapted for survival in a dry climate?

2. Desert plants have adapted several ingenious methods for survival in a dry climate. Some plants have a thick, waxy cuticle that helps prevent the loss of water. Others have small or needle-like leaves with few stomates. Many desert plants have extensive underground root systems that help absorb any precipitation that might fall. Others have thick stems that are adapted for the storage of water.

3. Why are the tropical rain forests ecologically important despite the fact that they occupy only 2% of the earth’s land surface area?

3. The tropical rain forests are ecologically important because of their tremendous biodiversity. More than 50% of the earth’s plant and animal life is found in this biome.

1. What is the effect of increased population growth on the environment?

Answer: Increased population growth creates added demands for the earth’s limited resources of energy, food, water, and living space. Furthermore, more people results in an increase in pollution and a decrease in biodiversity.

3. What are some of the major sources of man-made and natural pollution?

Answer: The major sources of man-made pollution are the burning of fossil fuels, industrial waste, pesticides, insecticides, fertilizer, and biological waste. Volcanic eruptions that emit ash and other particles are an example of a source of natural pollution.

4. How is pollution harmful to a person’s health? Answer: Air pollutants can cause respiratory problems such as bronchitis, asthma, and

lung cancer. Pollutants in water and soil can cause cancer in humans.

1. What is meant by exponential population growth?

1. Exponential population growth refers to the doubling of the population every few years.

2. How can scarce resources be preserved?

2. Scarce resources can be preserved by decreasing population growth, reducing the use of fossil fuels and through conservation of the environment. In addition, currently available resources can be reused and recycled.

3. What threats are posed by global warming?

3. Global warming has the potential of causing major disruptions in the world’s ecosystems. An increase in temperature can result in melting glaciers and rising sea levels. Changes in climate might occur that produce droughts in some areas and flooding in others. Additional threats are wildfires, reduced water supplies, reduced biodiversity, and crop failures.

1. What is conservation?

Answer: Conservation is concerned with the protection and maintenance of an ecosystem and its biological communities.

2. What are the most important steps that can be taken to help conserve and protect the environment?

Answer: The most important steps that can be taken to help conserve and protect the environment are reducing the rate of human population growth and striving toward negative population growth. In addition, reducing pollution and the use of fossil fuels, along with protecting open spaces and wildlife, helps to conserve resources.

3. What is biological pest control?

Answer: Biological pest control is the control of a pest population by nonchemical means (predators, parasites, animal-like protists, bacteria, and diseases) to destroy or control a pest population.

1. How can the water supply be conserved and maintained?

1. Water conservation can be achieved by reducing pollution from agriculture. Runoff from fertilizers, pesticides, and animal wastes are the main causes of water pollution. Control of point source pollution from factories, sewage treatment plants, and home septic tanks can also help preserve the water supply.

2. Why is the destruction of the rain forest for use as farmland not a good idea?

2. The soil in rain forests is acidic, low in nutrients, and needs to be heavily fertilized to grow crops. However, fertilizer is expensive and not often used by farmers in land that was once rain forest. As a result, the farmers get a low yield on their crop production. In the mean- time, this valuable resource (along with its diverse plant and animal life) is destroyed.

3. What are the advantages and disadvantages of biological pest controls?

3. Biological pest controls do not pollute the environment and do not kill helpful insects and birds because they target a specific pest population. Biological controls are harmless to humans. The disadvantage of biological pest controls is that they are expensive and often require repeated applications. In addition, biological controls generally target only one type of pest, unlike chemical controls whose action is more widespread.